Element-Specific Magnetization Dynamics in Co–Pt Alloys Induced by Strong Optical ExcitationClick to copy article linkArticle link copied!
- Igor Vaskivskyi*Igor Vaskivskyi*(I.V.) Email [email protected]Center for Memory and Recording Research, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0401, United StatesDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, SwedenMore by Igor Vaskivskyi
- Rameez Saeed MalikRameez Saeed MalikDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, SwedenMore by Rameez Saeed Malik
- Leandro SalemiLeandro SalemiDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, SwedenMore by Leandro Salemi
- Diego TurenneDiego TurenneDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, SwedenMore by Diego Turenne
- Ronny KnutRonny KnutDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, SwedenMore by Ronny Knut
- Jeffrey BrockJeffrey BrockCenter for Memory and Recording Research, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0401, United StatesMore by Jeffrey Brock
- Robert StefanuikRobert StefanuikDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, SwedenMore by Robert Stefanuik
- Johan SöderströmJohan SöderströmDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, SwedenMore by Johan Söderström
- Karel CarvaKarel CarvaFaculty of Mathematics and Physics, Department of Condensed Matter Physics, Charles University, Ke Karlovu 5, 121 16 Prague, Czech RepublicMore by Karel Carva
- Eric E. FullertonEric E. FullertonCenter for Memory and Recording Research, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0401, United StatesMore by Eric E. Fullerton
- Peter M. OppeneerPeter M. OppeneerDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, SwedenMore by Peter M. Oppeneer
- Olof KarisOlof KarisDepartment of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, SwedenMore by Olof Karis
- Hermann A. Dürr*Hermann A. Dürr*(H.A.D.) Email [email protected]Department of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, SwedenMore by Hermann A. Dürr
Abstract
Ever since its first observation, the microscopic origin of ultrafast magnetization dynamics has been actively debated. Even more questions arise when considering composite materials featuring a combination of intrinsic and proximity-induced magnetic moments. Currently, it is unknown whether the specific ultrafast dynamics of different sublattices in the popular ferromagnets consisting of 3d (Co, Fe) and 4d, 5d (Pd, Pt) transition metals are playing a crucial role in various effects, including all-optical magnetization switching. Here we investigate the element-specific dynamics of Co–Pt alloys on femtosecond and picosecond time scales using magneto-optical spectroscopy in the extended ultraviolet (EUV) region. Our results reveal that despite the proximity-induced nature of the magnetization of Pt atoms, the two sublattices in the alloy can have different responses to the optical excitation featuring distinct demagnetization rates. Additionally we show that it is important to consider the modification of magnetic anisotropy in opto-magnetic experiments as the vast majority of them are sensitive only to a single projection of the magnetic moment on the predefined axis, which may lead to experimental artifacts.
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License Summary*
You are free to share(copy and redistribute) this article in any medium or format and to adapt(remix, transform, and build upon) the material for any purpose, even commercially within the parameters below:
Creative Commons (CC): This is a Creative Commons license.
Attribution (BY): Credit must be given to the creator.
*Disclaimer
This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials.
License Summary*
You are free to share(copy and redistribute) this article in any medium or format and to adapt(remix, transform, and build upon) the material for any purpose, even commercially within the parameters below:
Creative Commons (CC): This is a Creative Commons license.
Attribution (BY): Credit must be given to the creator.
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Special Issue
Published as part of The Journal of Physical Chemistry virtual special issue “D. D. Sarma Festschrift”.
Introduction
Methods
Sample Growth and Characterization
Experimental Setup
DFT Calculations
Results and Discussion
Short-Time Dynamics and the Demagnetization
Remagnetization Dynamics
Conclusions
Acknowledgments
I.V., J.B., and E.E.F. acknowledge support by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under the X-ray Scattering Program Award DE-SC0017643. D.T., P.M.O., and H.A.D. acknowledge support from the Swedish Research Council (VR). P.M.O. acknowledges support from the K. and A. Wallenberg Foundation (Grant 2015.0060). The calculations were enabled by resources provided by the Swedish National Infrastructure for Computing (SNIC) at NSC Linköping, partially funded by VR through Grant Agreement 2018-05973.
References
This article references 41 other publications.
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- 5Ostler, T. A.; Barker, J.; Evans, R. F. L.; Chantrell, R. W.; Atxitia, U.; Chubykalo-Fesenko, O.; El Moussaoui, S.; Le Guyader, L.; Mengotti, E.; Heyderman, L. J. Ultrafast Heating as a Sufficient Stimulus for Magnetization Reversal in a Ferrimagnet. Nat. Commun. 2012, 3, 666, DOI: 10.1038/ncomms1666Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC383htlaquw%253D%253D&md5=71437326fefd4f5f70cc9849e5cd1f2bUltrafast heating as a sufficient stimulus for magnetization reversal in a ferrimagnetOstler T A; Barker J; Evans R F L; Chantrell R W; Atxitia U; Chubykalo-Fesenko O; El Moussaoui S; Le Guyader L; Mengotti E; Heyderman L J; Nolting F; Tsukamoto A; Itoh A; Afanasiev D; Ivanov B A; Kalashnikova A M; Vahaplar K; Mentink J; Kirilyuk A; Rasing Th; Kimel A VNature communications (2012), 3 (), 666 ISSN:.The question of how, and how fast, magnetization can be reversed is a topic of great practical interest for the manipulation and storage of magnetic information. It is generally accepted that magnetization reversal should be driven by a stimulus represented by time-non-invariant vectors such as a magnetic field, spin-polarized electric current, or cross-product of two oscillating electric fields. However, until now it has been generally assumed that heating alone, not represented as a vector at all, cannot result in a deterministic reversal of magnetization, although it may assist this process. Here we show numerically and demonstrate experimentally a novel mechanism of deterministic magnetization reversal in a ferrimagnet driven by an ultrafast heating of the medium resulting from the absorption of a sub-picosecond laser pulse without the presence of a magnetic field.
- 6Alebrand, S.; Gottwald, M.; Hehn, M.; Steil, D.; Cinchetti, M.; Lacour, D.; Fullerton, E. E.; Aeschlimann, M.; Mangin, S. Light-Induced Magnetization Reversal of High-Anisotropy TbCo Alloy Films. Appl. Phys. Lett. 2012, 101, 162408, DOI: 10.1063/1.4759109Google Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsFCnsbfL&md5=8647bc1b417835c1cf5febb424947e52Light-induced magnetization reversal of high-anisotropy TbCo alloy filmsAlebrand, Sabine; Gottwald, Matthias; Hehn, Michel; Steil, Daniel; Cinchetti, Mirko; Lacour, Daniel; Fullerton, Eric E.; Aeschlimann, Martin; Mangin, StephaneApplied Physics Letters (2012), 101 (16), 162408/1-162408/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Magnetization reversal using circularly polarized light provides a way to control magnetization without any external magnetic field and has the potential to revolutionize magnetic data storage. However, to reach ultra-high d. data storage, high anisotropy media providing thermal stability are needed. Here, we evidence all-optical magnetization switching for different TbxCo1-x ferrimagnetic alloy compns. using fs- and ps-laser pulses and demonstrate all-optical switching for films with anisotropy fields reaching 6 T corresponding to anisotropy consts. of 3 × 106 ergs/cm3. Optical magnetization switching is obsd. only for alloy compns. where the compensation temp. can be reached through sample heating. (c) 2012 American Institute of Physics.
- 7Radu, I.; Vahaplar, K.; Stamm, C.; Kachel, T.; Pontius, N.; Dürr, H. A.; Ostler, T. A.; Barker, J.; Evans, R. F. L.; Chantrell, R. W. Transient Ferromagnetic-like State Mediating Ultrafast Reversal of Antiferromagnetically Coupled Spins. Nature 2011, 472, 205– 208, DOI: 10.1038/nature09901Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXjvFOnt7o%253D&md5=e4cf37e8f1a500275ad5aba0f13d6618Transient ferromagnetic-like state mediating ultrafast reversal of antiferromagnetically coupled spinsRadu, I.; Vahaplar, K.; Stamm, C.; Kachel, T.; Pontius, N.; Duerr, H. A.; Ostler, T. A.; Barker, J.; Evans, R. F. L.; Chantrell, R. W.; Tsukamoto, A.; Itoh, A.; Kirilyuk, A.; Rasing, Th.; Kimel, A. V.Nature (London, United Kingdom) (2011), 472 (7342), 205-208CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)Ferromagnetic or antiferromagnetic spin ordering is governed by the exchange interaction, the strongest force in magnetism. Understanding spin dynamics in magnetic materials is an issue of crucial importance for progress in information processing and recording technol. Usually the dynamics are studied by observing the collective response of exchange-coupled spins, i.e., spin resonances, after an external perturbation by a pulse of magnetic field, current or light. The periods of the corresponding resonances range from one nanosecond for ferromagnets down to one picosecond for antiferromagnets. However, virtually nothing is known about the behavior of spins in a magnetic material after being excited on a timescale faster than that corresponding to the exchange interaction (10-100 fs), i.e., in a non-adiabatic way. Here we use the element-specific technique X-ray magnetic CD to study spin reversal in GdFeCo that is optically excited on a timescale pertinent to the characteristic time of the exchange interaction between Gd and Fe spins. We unexpectedly find that the ultrafast spin reversal in this material, where spins are coupled antiferromagnetically, occurs by way of a transient ferromagnetic-like state. Following the optical excitation, the net magnetizations of the Gd and Fe sublattices rapidly collapse, switch their direction and rebuild their net magnetic moments at substantially different timescales; the net magnetic moment of the Gd sublattice is found to reverse within 1.5 ps, which is substantially slower than the Fe reversal time of 300 fs. Consequently, a transient state characterized by a temporary parallel alignment of the net Gd and Fe moments emerges, despite their ground-state antiferromagnetic coupling. These surprising observations, supported by atomistic simulations, provide a concept for the possibility of manipulating magnetic order on the timescale of the exchange interaction.
- 8Graves, C. E.; Reid, A. H.; Wang, T.; Wu, B.; de Jong, S.; Vahaplar, K.; Radu, I.; Bernstein, D. P.; Messerschmidt, M.; Müller, L. Nanoscale Spin Reversal by Non-Local Angular Momentum Transfer Following Ultrafast Laser Excitation in Ferrimagnetic GdFeCo. Nat. Mater. 2013, 12, 293– 298, DOI: 10.1038/nmat3597Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXktVKmt7Y%253D&md5=5e2ed422686dde48187fd4bec1a6dfa2Nanoscale spin reversal by non-local angular momentum transfer following ultrafast laser excitation in ferrimagnetic GdFeCoGraves, C. E.; Reid, A. H.; Wang, T.; Wu, B.; de Jong, S.; Vahaplar, K.; Radu, I.; Bernstein, D. P.; Messerschmidt, M.; Mueller, L.; Coffee, R.; Bionta, M.; Epp, S. W.; Hartmann, R.; Kimmel, N.; Hauser, G.; Hartmann, A.; Holl, P.; Gorke, H.; Mentink, J. H.; Tsukamoto, A.; Fognini, A.; Turner, J. J.; Schlotter, W. F.; Rolles, D.; Soltau, H.; Strueder, L.; Acremann, Y.; Kimel, A. V.; Kirilyuk, A.; Rasing, Th.; Stoehr, J.; Scherz, A. O.; Duerr, H. A.Nature Materials (2013), 12 (4), 293-298CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)Ultrafast laser techniques have revealed extraordinary spin dynamics in magnetic materials that equil. descriptions of magnetism cannot explain. Particularly important for future applications is understanding non-equil. spin dynamics following laser excitation on the nanoscale, yet the limited spatial resoln. of optical laser techniques has impeded such nanoscale studies. Here we present ultrafast diffraction expts. with an x-ray laser that probes the nanoscale spin dynamics following optical laser excitation in the ferrimagnetic alloy GdFeCo, which exhibits macroscopic all-optical switching. Our study reveals that Gd24Fe66.5Co9.5 displays nanoscale chem. and magnetic inhomogeneities that affect the spin dynamics. In particular, we observe Gd spin reversal in Gd-rich nanoregions within the 1st picosecond driven by the non-local transfer of angular momentum from larger adjacent Fe-rich nanoregions. These results suggest that a magnetic material's microstructure can be engineered to control transient laser-excited spins, potentially allowing faster (∼ 1 ps) spin reversal than in present technologies.
- 9Liu, T.-M.; Wang, T.; Reid, A. H.; Savoini, M.; Wu, X.; Koene, B.; Granitzka, P.; Graves, C. E.; Higley, D. J.; Chen, Z. Nanoscale Confinement of All-Optical Magnetic Switching in TbFeCo - Competition with Nanoscale Heterogeneity. Nano Lett. 2015, 15, 6862– 6868, DOI: 10.1021/acs.nanolett.5b02743Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC287msV2lug%253D%253D&md5=9f03b0bd0721e68492cb2c0ad89e3f2bNanoscale Confinement of All-Optical Magnetic Switching in TbFeCo--Competition with Nanoscale HeterogeneityLiu Tian-Min; Wang Tianhan; Reid Alexander H; Granitzka Patrick; Graves Catherine E; Higley Daniel J; Chen Zhao; Scherz Andreas; Stohr Joachim; Durr Hermann A; Savoini Matteo; Koene Benny; Kimel Alexey V; Kirilyuk Andrei; Rasing Theo; Wu Xiaofei; Razinskas Gary; Hecht Bert; Wu Xiaofei; Granitzka Patrick; Hantschmann Markus; Tsukamoto ArataNano letters (2015), 15 (10), 6862-8 ISSN:.Single femtosecond optical laser pulses, of sufficient intensity, are demonstrated to reverse magnetization in a process known as all-optical switching. Gold two-wire antennas are placed on the all-optical switching film TbFeCo. These structures are resonant with the optical field, and they create a field enhancement in the near-field which confines the area where optical switching can occur. The magnetic switching that occurs around and below the antenna is imaged using resonant X-ray holography and magnetic circular dichroism. The results not only show the feasibility of controllable switching with antenna assistance but also demonstrate the highly inhomogeneous nature of the switching process, which is attributed to the process depending on the material's heterogeneity.
- 10Mangin, S.; Gottwald, M.; Lambert, C.-H.; Steil, D.; Uhlíř, V.; Pang, L.; Hehn, M.; Alebrand, S.; Cinchetti, M.; Malinowski, G. Engineered Materials for All-Optical Helicity-Dependent Magnetic Switching. Nat. Mater. 2014, 13, 286– 292, DOI: 10.1038/nmat3864Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXisFOkurs%253D&md5=ea1789463dff598c75d325fbdfdc6faeEngineered materials for all-optical helicity-dependent magnetic switchingMangin, S.; Gottwald, M.; Lambert, C.-H.; Steil, D.; Uhlir, V.; Pang, L.; Hehn, M.; Alebrand, S.; Cinchetti, M.; Malinowski, G.; Fainman, Y.; Aeschlimann, M.; Fullerton, E. E.Nature Materials (2014), 13 (3), 286-292CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)The possibility of manipulating magnetic systems without applied magnetic fields have attracted growing attention over the past fifteen years. The low-power manipulation of the magnetization, preferably at ultrashort timescales, has become a fundamental challenge with implications for future magnetic information memory and storage technologies. Here the authors explore the optical manipulation of the magnetization in engineered magnetic materials. All-optical helicity-dependent switching (AO-HDS) can be obsd. not only in selected rare earth-transition metal (RE-TM) alloy films but also in a much broader variety of materials, including RE-TM alloys, multilayers and heterostructures. Further RE-free Co-Ir-based synthetic ferrimagnetic heterostructures designed to mimic the magnetic properties of RE-TM alloys also exhibit AO-HDS. These results challenge present theories of AO-HDS and provide a pathway to engineering materials for future applications based on all-optical control of magnetic order.
- 11Lambert, C.-H.; Mangin, S.; Varaprasad, B. S. D. C. S.; Takahashi, Y. K.; Hehn, M.; Cinchetti, M.; Malinowski, G.; Hono, K.; Fainman, Y.; Aeschlimann, M. All-Optical Control of Ferromagnetic Thin Films and Nanostructures. Science 2014, 345, 1337– 1340, DOI: 10.1126/science.1253493Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsV2qtL%252FK&md5=6bca6a08b9677d61de969426f9e820a0All-optical control of ferromagnetic thin films and nanostructuresLambert, C.-H.; Mangin, S.; Varaprasad, B. S. D. Ch. S.; Takahashi, Y. K.; Hehn, M.; Cinchetti, M.; Malinowski, G.; Hono, K.; Fainman, Y.; Aeschlimann, M.; Fullerton, E. E.Science (Washington, DC, United States) (2014), 345 (6202), 1337-1340CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The interplay of light and magnetism allowed light to be used as a probe of magnetic materials. Now the focus has shifted to use polarized light to alter or manipulate magnetism. Here, we demonstrate optical control of ferromagnetic materials ranging from magnetic thin films to multilayers and even granular films being explored for ultra-high-d. magnetic recording. Our finding shows that optical control of magnetic materials is a much more general phenomenon than previously assumed and may have a major impact on data memory and storage industries through the integration of optical control of ferromagnetic bits.
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- 15Vomir, M.; Albrecht, M.; Bigot, J.-Y. Single Shot All Optical Switching of Intrinsic Micron Size Magnetic Domains of a Pt/Co/Pt Ferromagnetic Stack. Appl. Phys. Lett. 2017, 111, 242404, DOI: 10.1063/1.5010915Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFyjtrfE&md5=a42ef077535a3f3f5648a36dfa921b96Single shot all optical switching of intrinsic micron size magnetic domains of a Pt/Co/Pt ferromagnetic stackVomir, M.; Albrecht, M.; Bigot, J.-Y.Applied Physics Letters (2017), 111 (24), 242404/1-242404/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)We demonstrate that magnetization reversal in a ferromagnetic Pt/Co/Pt stack can be induced by a single femtosecond laser pulse. We find that the size of the switched spot is comparable to the size of the intrinsic magnetic domains. It requires an absorbed energy d. of ∼4 mJ cm-2, beyond which the excited spot fragments into a multidomain structure. The switching process can be toggled with sequential laser pulses and is helicity-independent. Furthermore, the dynamics of the magnetization reversal occurs in a timescale less than one microsecond. These results suggest that all-optical switching in ferromagnetic films requires that the laser spot matches with the specific domain sizes. (c) 2017 American Institute of Physics.
- 16Gorchon, J.; Lambert, C.-H.; Yang, Y.; Pattabi, A.; Wilson, R. B.; Salahuddin, S.; Bokor, J. Single Shot Ultrafast All Optical Magnetization Switching of Ferromagnetic Co/Pt Multilayers. Appl. Phys. Lett. 2017, 111, 042401, DOI: 10.1063/1.4994802Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1WltL7M&md5=47fad5775bd7f94b609c7aa65355a553Single shot ultrafast all optical magnetization switching of ferromagnetic Co/Pt multilayersGorchon, Jon; Lambert, Charles-Henri; Yang, Yang; Pattabi, Akshay; Wilson, Richard B.; Salahuddin, Sayeef; Bokor, JeffreyApplied Physics Letters (2017), 111 (4), 042401/1-042401/5CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)A single femto-second optical pulse can fully reverse the magnetization of a film within picoseconds. Such fast operation hugely increases the range of application of magnetic devices. However, so far, this type of ultrafast switching was restricted to ferri-magnetic GdFeCo films. In contrast, all optical switching of ferro-magnetic films require multiple pulses, thereby being slower and less energy efficient. Here, the authors demonstrate magnetization switching induced by a single laser pulse in various ferromagnetic Co/Pt multilayers grown on GdFeCo, by exploiting the exchange coupling between the two magnetic films. Table-top depth-sensitive time-resolved magneto-optical expts. show that the Co/Pt magnetization switches within 7 ps. This coupling approach will allow ultrafast control of a variety of magnetic films, which is crit. for applications. (c) 2017 American Institute of Physics.
- 17Igarashi, J.; Remy, Q.; Iihama, S.; Malinowski, G.; Hehn, M.; Gorchon, J.; Hohlfeld, J.; Fukami, S.; Ohno, H.; Mangin, S. Engineering Single-Shot All-Optical Switching of Ferromagnetic Materials. Nano Lett. 2020, 20, 8654– 8660, DOI: 10.1021/acs.nanolett.0c03373Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXitlyrsr3F&md5=5734addb6249c587e45ca0d10f41906eEngineering Single-Shot All-Optical Switching of Ferromagnetic MaterialsIgarashi, Junta; Remy, Quentin; Iihama, Satoshi; Malinowski, Gregory; Hehn, Michel; Gorchon, Jon; Hohlfeld, Julius; Fukami, Shunsuke; Ohno, Hideo; Mangin, StephaneNano Letters (2020), 20 (12), 8654-8660CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Since it was recently demonstrated in a spin-valve structure, magnetization reversal of a ferromagnetic layer using a single ultrashort optical pulse has attracted attention for future ultrafast and energy-efficient magnetic storage or memory devices. However, the mechanism and the role of the magnetic properties of the ferromagnet as well as the time scale of the magnetization switching are not understood. Here, we investigate single-shot all-optical magnetization switching in a GdFeCo/Cu/[CoxNi1-x/Pt] spin-valve structure. We demonstrate that the threshold fluence for switching both the GdFeCo and the ferromagnetic layer depends on the laser pulse duration and the thickness and the Curie temp. of the ferromagnetic layer. CoxNi1-x (x = 0.2, 0.3, 0.4, 0.6, 0.8, 1). We are able to explain most of the exptl. results using a phenomenol. model. This work provides a way to engineer ferromagnetic materials for energy efficient single-shot all-optical magnetization switching.
- 18Cornelissen, T. D.; Córdoba, R.; Koopmans, B. Microscopic Model for All Optical Switching in Ferromagnets. Appl. Phys. Lett. 2016, 108, 142405, DOI: 10.1063/1.4945660Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XlslWltrw%253D&md5=e7efe3c1addaf31097cbb75a2f43de47Microscopic model for all optical switching in ferromagnetsCornelissen, T. D.; Cordoba, R.; Koopmans, B.Applied Physics Letters (2016), 108 (14), 142405/1-142405/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)The microscopic mechanism behind the all optical switching (AOS) in ferromagnets has triggered intense scientific debate. Here, the microscopic three-temp. model is utilized to describe AOS in a perpendicularly magnetized ferromagnetic Co/Pt system. We demonstrate that AOS in such a ferromagnet can be explained with the Inverse Faraday Effect (IFE). The influence of the strength and lifetime of the IFE induced field pulse on the switching process are investigated. We found that because of strong spin-orbit coupling, the minimal lifetime of the IFE needed to obtain switching is of the order of 0.1 ps, which is shorter than previously assumed. Moreover, spatial images of the domain pattern after AOS in Co/Pt, as well as their dependence on applying an opposite magnetic field, are qual. reproduced. (c) 2016 American Institute of Physics.
- 19Yamamoto, K.; Kubota, Y.; Suzuki, M.; Hirata, Y.; Carva, K.; Berritta, M.; Takubo, K.; Uemura, Y.; Fukaya, R.; Tanaka, K. Ultrafast Demagnetization of Pt Magnetic Moment in L10-FePt Probed by Magnetic Circular Dichroism at a Hard x-Ray Free Electron Laser. New J. Phys. 2019, 21, 123010, DOI: 10.1088/1367-2630/ab5ac2Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhs1yiurbK&md5=80e45e0e104cfb68f83e819087c5215dUltrafast demagnetization of Pt magnetic moment in L10-FePt probed by magnetic circular dichroism at a hard x-ray free electron laserYamamoto, Kohei; Kubota, Yuya; Suzuki, Motohiro; Hirata, Yasuyuki; Carva, Karel; Berritta, Marco; Takubo, Kou; Uemura, Yohei; Fukaya, Ryo; Tanaka, Kenta; Nishimura, Wataru; Ohkochi, Takuo; Katayama, Tetsuo; Togashi, Tadashi; Tamasaku, Kenji; Yabashi, Makina; Tanaka, Yoshihito; Seki, Takeshi; Takanashi, Koki; Oppeneer, Peter M.; Wadati, HirokiNew Journal of Physics (2019), 21 (Dec.), 123010CODEN: NJOPFM; ISSN:1367-2630. (IOP Publishing Ltd.)Unraveling the origin of ultrafast demagnetization in multisublattice ferromagnetic materials requires femtosecond x-ray techniques to trace the magnetic moment dynamics on individual elements, but this could not yet be achieved in the hard x-ray regime.Wedemonstrate here the first ultrafast demagnetization dynamics in the ferromagnetic heavy 5d-transition metal Pt using circularlypolarized hard x-rays at an x-ray free electron laser (XFEL). The decay time of laser-induced demagnetization of L10-FePt is detd. to be τPt = 0.61 ± 0.04 ps using time-resolved x-ray magnetic CD at the PtL3 edge, whereas magneto-optical Kerr measurements indicate the decay time for the totalmagnetization as τtotal < 0.1 ps. A transientmagnetic statewith a photo-modulated ratio of the 3d and 5d magnetic moments is demonstrated for pump-probe delays larger than 1 ps. We explain this distinct photo-modulated transient magnetic state by the induced-moment behavior of the Pt atom and the x-ray probing depth. Our findings pave the way for the future use of XFELs to disentangle at. spin dynamics contributions.
- 20Hofherr, M.; Moretti, S.; Shim, J.; Häuser, S.; Safonova, N. Y.; Stiehl, M.; Ali, A.; Sakshath, S.; Kim, J. W.; Kim, D. H. Induced versus Intrinsic Magnetic Moments in Ultrafast Magnetization Dynamics. Phys. Rev. B: Condens. Matter Mater. Phys. 2018, 98, 174419, DOI: 10.1103/PhysRevB.98.174419Google ScholarThere is no corresponding record for this reference.
- 21Kuiper, K. C.; Roth, T.; Schellekens, A. J.; Schmitt, O.; Koopmans, B.; Cinchetti, M.; Aeschlimann, M. Spin-Orbit Enhanced Demagnetization Rate in Co/Pt-Multilayers. Appl. Phys. Lett. 2014, 105, 202402, DOI: 10.1063/1.4902069Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhvFKktrjN&md5=40845ad6285c3be2486baad90f3325e0Spin-orbit enhanced demagnetization rate in Co/Pt-multilayersKuiper, K. C.; Roth, T.; Schellekens, A. J.; Schmitt, O.; Koopmans, B.; Cinchetti, M.; Aeschlimann, M.Applied Physics Letters (2014), 105 (20), 202402/1-202402/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)In order to explore the role of enhanced spin-orbit interactions on the laser-induced ultrafast magnetization dynamics, we performed a comparative study on Co thin films and Co/Pt multilayers. We show that the presence of the Co/Pt interfaces gives rise to a 3-fold faster demagnetization upon femtosecond laser heating. Exptl. data for a wide range of laser fluences are analyzed using the microscopic 3-temp. model. We find that the Elliott-Yafet spin-flip scattering in the multilayer structure is increased by at least a factor of four with respect to the elementary Co film. (c) 2014 American Institute of Physics.
- 22Hecker, M.; Oppeneer, P. M.; Valencia, S.; Mertins, H.-Ch.; Schneider, C. M. Soft X-Ray Magnetic Reflection Spectroscopy at the 3p Absorption Edges of Thin Fe Films. J. Electron Spectrosc. Relat. Phenom. 2005, 144–147, 881– 884, DOI: 10.1016/j.elspec.2005.01.151Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXjsVymt7g%253D&md5=de8d6b1366d4e0d5e502217fcf589ff3Soft X-ray magnetic reflection spectroscopy at the 3p absorption edges of thin Fe filmsHecker, M.; Oppeneer, P. M.; Valencia, S.; Mertins, H.-Ch.; Schneider, C. M.Journal of Electron Spectroscopy and Related Phenomena (2005), 144-147 (), 881-884CODEN: JESRAW; ISSN:0368-2048. (Elsevier B.V.)Soft X-ray magnetic reflection spectroscopy with linearly polarized light was used to investigate thin Fe films close to their 3p absorption edges. The high reflectivity in this spectral range enables one to measure magnetic signals in a wide angular range up to near-normal incidence. A strong amplification of the T-MOKE (transversal magneto-optical Kerr effect) asymmetry ratio occurs close to scattering angles of θ ∼ 45° and leads to huge magnetic signals of more than 50%. Utilizing these high signals, the course of the in-plane sample magnetization during the hysteresis cycle was detd. from the variation of the hysteresis loops with the measurement geometry.
- 23Willems, F.; von Korff Schmising, C.; Strüber, C.; Schick, D.; Engel, D. W.; Dewhurst, J. K.; Elliott, P.; Sharma, S.; Eisebitt, S. Optical Inter-Site Spin Transfer Probed by Energy and Spin-Resolved Transient Absorption Spectroscopy. Nat. Commun. 2020, 11, 871, DOI: 10.1038/s41467-020-14691-5Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXkvFajtbo%253D&md5=f62879c503d177cd1f129699a29b53f1Optical inter-site spin transfer probed by energy and spin-resolved transient absorption spectroscopyWillems, Felix; von Korff Schmising, Clemens; Strueber, Christian; Schick, Daniel; Engel, Dieter W.; Dewhurst, J. K.; Elliott, Peter; Sharma, Sangeeta; Eisebitt, StefanNature Communications (2020), 11 (1), 871CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)Abstr.: Optically driven spin transport is the fastest and most efficient process to manipulate macroscopic magnetization as it does not rely on secondary mechanisms to dissipate angular momentum. In the present work, we show that such an optical inter-site spin transfer (OISTR) from Pt to Co emerges as a dominant mechanism governing the ultrafast magnetization dynamics of a CoPt alloy. To demonstrate this, we perform a joint theor. and exptl. investigation to det. the transient changes of the helicity dependent absorption in the extreme UV spectral range. We show that the helicity dependent absorption is directly related to changes of the transient spin-split d. of states, allowing us to link the origin of OISTR to the available minority states above the Fermi level. This makes OISTR a general phenomenon in optical manipulation of multi-component magnetic systems.
- 24Plogmaker, S.; Terschlüsen, J. A.; Krebs, N.; Svanqvist, M.; Forsberg, J.; Cappel, U. B.; Rubensson, J.-E.; Siegbahn, H.; Söderström, J. HELIOS—A Laboratory Based on High-Order Harmonic Generation of Extreme Ultraviolet Photons for Time-Resolved Spectroscopy. Rev. Sci. Instrum. 2015, 86, 123107, DOI: 10.1063/1.4937463Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitVKjtLbL&md5=e7b0980a3b75e46eeed6c78be3548ae7HELIOS - A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopyPlogmaker, S.; Terschlusen, J. A.; Krebs, N.; Svanqvist, M.; Forsberg, J.; Cappel, U. B.; Rubensson, J.-E.; Siegbahn, H.; Soederstroem, J.Review of Scientific Instruments (2015), 86 (12), 123107/1-123107/9CODEN: RSINAK; ISSN:0034-6748. (American Institute of Physics)The HELIOS (High Energy Laser Induced Overtone Source) lab., an inhouse high-order harmonic generation facility which generates extreme UV (XUV) photon pulses at 15-70 eV with monochromatized XUV pulse lengths <35 fs, is presented. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe expts. with wavelengths ranging from 240 nm to 20,000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, 1st monochromatized spectra are shown with an intensity of 2 × 1010 photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is <25 fs after monochromatization. (c) 2015 American Institute of Physics.
- 25Stefanuik, R.; Knut, R.; Jana, S.; Terschlüsen, J. A.; Sandell, A.; Söderström, J. Developments and Enhancements to the HELIOS Pump Probe System. J. Electron Spectrosc. Relat. Phenom. 2018, 224, 33– 37, DOI: 10.1016/j.elspec.2017.09.004Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsFCqs7rE&md5=ed1d38a79c595528783e0e81d228a9a4Developments and enhancements to the HELIOS pump probe systemStefanuik, R.; Knut, R.; Jana, S.; Terschlusen, J. A.; Sandell, A.; Soederstroem, J.Journal of Electron Spectroscopy and Related Phenomena (2018), 224 (), 33-37CODEN: JESRAW; ISSN:0368-2048. (Elsevier B.V.)In this progress report we describe several design improvements that have been implemented at the HELIOS lab., as well as presenting the output characteristics that have been measured as a result. The main focus will be on the redesign of the gas cell, which has enhanced the photon flux of the XUV probe beam. Also, a frequency trippler utilizing sum frequency generation has been installed at the end of the pump line, which increases the photon flux available for both 3.1 eV (400 nm) and 4.66 eV (266 nm) applications without significant increment in the pulse width of the pump.
- 26Jana, S.; Terschlüsen, J. A.; Stefanuik, R.; Plogmaker, S.; Troisi, S.; Malik, R. S.; Svanqvist, M.; Knut, R.; Söderström, J.; Karis, O. A Setup for Element Specific Magnetization Dynamics Using the Transverse Magneto-Optic Kerr Effect in the Energy Range of 30–72 EV. Rev. Sci. Instrum. 2017, 88, 033113, DOI: 10.1063/1.4978907Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXltlKku7s%253D&md5=753607eba9473ed8e18736eac2fe50aeA setup for element specific magnetization dynamics using the transverse magneto-optic Kerr effect in the energy range of 30-72 eVJana, S.; Terschlusen, J. A.; Stefanuik, R.; Plogmaker, S.; Troisi, S.; Malik, R. S.; Svanqvist, M.; Knut, R.; Soederstroem, J.; Karis, O.Review of Scientific Instruments (2017), 88 (3), 033113/1-033113/8CODEN: RSINAK; ISSN:0034-6748. (American Institute of Physics)In this paper, we present a spectrometer that is designed for element-specific and time-resolved transverse magneto-optic Kerr effect expts. at the high-harmonic generation pump-probe facility High Energy Laser Induced Overtone Source (HELIOS) lab. HELIOS delivers photons with energies between 30 eV and 72 eV with an overall time resoln. of less than 40 fs. The spectrometer is based on a Rowland-circle geometry and allows for simultaneous measurements of all magnetic transition-metal elements. The setup also features easy sample transfer and alignment, and it combines high photon throughput, optimized data acquisition, and a fast switching of the magnetic field at the sample. The spectrometer performance is demonstrated by measuring the ultrafast demagnetization of permalloy. Our data are, for all practical purposes, identical to what have been reported in the earlier high-order harmonic generation work of a similar sample by Mathias et al. [Proc. Natl. Acad. Sci. U. S. A. 109, 4792-4797 (2012)], however, obtained within 15% of the acquisition time compared to their study. Furthermore, our data show a shift of the demagnetization curve of Ni relative to Fe, which has previously been interpreted as a delay of the Ni demagnetization to that of Fe [S. Mathias et al., Proc. Natl. Acad. Sci. U. S. A. 109, 4792-4797 (2012)]. (c) 2017 American Institute of Physics.
- 27Blaha, P.; Schwarz, K.; Madsen, G.; Kvasnicka, D.; Luitz, J. WIEN2k: An Augmented Plane Wave plus Local Orbitals Program for Calculating Crystal Properties; Technische Universität Wien: Vienna, Austria, 2001.Google ScholarThere is no corresponding record for this reference.
- 28Valencia, S.; Kleibert, A.; Gaupp, A.; Rusz, J.; Legut, D.; Bansmann, J.; Gudat, W.; Oppeneer, P. M. Quadratic X-Ray Magneto-Optical Effect upon Reflection in a Near-Normal-Incidence Configuration at the M Edges of 3d-Transition Metals. Phys. Rev. Lett. 2010, 104, 187401, DOI: 10.1103/PhysRevLett.104.187401Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXmslKmtbw%253D&md5=08a857aaea9718f3b7ab18973670ddbdQuadratic X-ray magneto-optical effect upon reflection in a near-normal-incidence configuration at the M edges of 3d-transition metalsValencia, S.; Kleibert, A.; Gaupp, A.; Rusz, J.; Legut, D.; Bansmann, J.; Gudat, W.; Oppeneer, P. M.Physical Review Letters (2010), 104 (18), 187401/1-187401/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)The authors obsd. a quadratic x-ray magneto-optical effect in near-normal-incidence reflection at the M edges of Fe. The effect appears as the magnetically induced rotation of ∼0.1° of the polarization plane of linearly polarized x-ray radiation upon reflection. A comparison of the measured rotation spectrum with results from x-ray magnetic linear dichroism data demonstrates that this is the 1st observation of the Schaefer-Hubert effect in the x-ray regime. Ab initio d.-functional theory calcns. reveal that hybridization effects of the 3p core states necessarily need to be considered when interpreting exptl. data. The discovered magneto-x-ray effect holds promise for future ultrafast and element-selective studies of ferromagnetic as well as antiferromagnetic materials.
- 29Turek, I.; Drchal, V.; Kudrnovsky, J.; Sob, M.; Weinberger, P. Electronic Structure of Disordered Alloys, Surfaces and Interfaces; Springer: Boston, MA, 1997.Google ScholarThere is no corresponding record for this reference.
- 30Staunton, J.; Gyorffy, B. L.; Pindor, A. J.; Stocks, G. M.; Winter, H. Electronic Structure of Metallic Ferromagnets above the Curie Temperature. J. Phys. F: Met. Phys. 1985, 15, 1387, DOI: 10.1088/0305-4608/15/6/019Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2MXktFGksLY%253D&md5=afcd21ab6ff9ab510f710c8bb6b866c7Electronic structure of metallic ferromagnets above the Curie temperatureStaunton, J.; Gyorffy, B. L.; Pindor, A. J.; Stocks, G. M.; Winter, H.Journal of Physics F: Metal Physics (1985), 15 (6), 1387-404CODEN: JPFMAT; ISSN:0305-4608.The electronic structure of Fe and Ni above their Curie temps. in their disordered local moment (DLM) states is described as a function of wavevector k and energy ε. The Bloch spectral function, ‾A(k, ε), averaged over the orientational configurations of the local moments, is calcd. at selected points in the Brillouin zone and the shape and smearing of the "Fermi surface" is detd. Bcc. Fe, with a local moment of 1.9 μB, can show an exchange splitting at some points, while in other regions of the Brillouin zone no such splitting occurs. For comparison fcc. Fe, which also supports a substantial local moment, is also studied. It has similar features, but the smearing of the "bands" is more pronounced. On the other hand, the electronic structure of Ni is quite different; it shows no such local exchange splitting, but is able to support a small local moment of 0.2 μB. The resulting picture for the electronic structure of Ni is that of a paramagnetic smeared "Stoner-Wohlfarth" model.
- 31Wagenknecht, D.; Šmejkal, L.; Kašpar, Z.; Sinova, J.; Jungwirth, T.; Kudrnovský, J.; Carva, K.; Turek, I. Temperature-Dependent Resistivity and Anomalous Hall Effect in NiMnSb from First Principles. Phys. Rev. B: Condens. Matter Mater. Phys. 2019, 99, 174433, DOI: 10.1103/PhysRevB.99.174433Google ScholarThere is no corresponding record for this reference.
- 32Shishidou, T.; Imada, S.; Muro, T.; Oda, F.; Kimura, A.; Suga, S.; Miyahara, T.; Kanomata, T.; Kaneko, T. Strong Fano Effect in the Magnetic Circular Dichroism of the Pt N6,7 Core Absorption of Ferromagnetic CoPt3. Phys. Rev. B: Condens. Matter Mater. Phys. 1997, 55, 3749– 3756, DOI: 10.1103/PhysRevB.55.3749Google ScholarThere is no corresponding record for this reference.
- 33Willems, F.; Smeenk, C. T. L.; Zhavoronkov, N.; Kornilov, O.; Radu, I.; Schmidbauer, M.; Hanke, M.; von Korff Schmising, C.; Vrakking, M. J. J.; Eisebitt, S. Probing Ultrafast Spin Dynamics with High-Harmonic Magnetic Circular Dichroism Spectroscopy. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 92, 220405, DOI: 10.1103/PhysRevB.92.220405Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XkvVWhsrs%253D&md5=32fd089d1a4f9f8727b5c35f0176049bProbing ultrafast spin dynamics with high-harmonic magnetic circular dichroism spectroscopyWillems, F.; Smeenk, C. T. L.; Zhavoronkov, N.; Kornilov, O.; Radu, I.; Schmidbauer, M.; Hanke, M.; von Korff Schmising, C.; Vrakking, M. J. J.; Eisebitt, S.Physical Review B: Condensed Matter and Materials Physics (2015), 92 (22), 220405/1-220405/5CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)Magnetic CD in the extreme UV (XUV) spectral range is a powerful technique for element-specific probing of magnetization in multicomponent magnetic alloys and multilayers. We combine a high-harmonic generation source with a λ/4 phase shifter to obtain circularly polarized XUV femtosecond pulses for ultrafast magnetization studies. We report on simultaneously measured resonant magnetic CD (MCD) of Co and Ni at their resp. M2,3 edges and of Pt at its O edge, originating from interface magnetism. We present a time-resolved MCD absorption measurement of a thin magnetic Pt/Co/Pt film, showing simultaneous demagnetization of Co and Pt on a femtosecond time scale.
- 34Yamamoto, K.; Moussaoui, S. E.; Hirata, Y.; Yamamoto, S.; Kubota, Y.; Owada, S.; Yabashi, M.; Seki, T.; Takanashi, K.; Matsuda, I. Element-Selectively Tracking Ultrafast Demagnetization Process in Co/Pt Multilayer Thin Films by the Resonant Magneto-Optical Kerr Effect. Appl. Phys. Lett. 2020, 116, 172406, DOI: 10.1063/5.0005393Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXosVylsLo%253D&md5=598ccaae0f43556419b57375fe9f7bb4Element-selectively tracking ultrafast demagnetization process in Co/Pt multilayer thin films by the resonant magneto-optical Kerr effectYamamoto, Kohei; Moussaoui, Souliman El; Hirata, Yasuyuki; Yamamoto, Susumu; Kubota, Yuya; Owada, Shigeki; Yabashi, Makina; Seki, Takeshi; Takanashi, Koki; Matsuda, Iwao; Wadati, HirokiApplied Physics Letters (2020), 116 (17), 172406/1-172406/5CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)We examd. the photo-induced dynamics of ferromagnetic Co/Pt thin films exhibiting perpendicular magnetic anisotropy by means of the resonant polar magneto-optical Kerr effect with element specificity. The investigation was conducted at Pt N6,7 and Co M2,3 edges using an x-ray free electron laser. The obtained results showed a clear element dependence of photo-induced demagnetization time scales: τCodemag. = 80±60 fs and τPtdemag. = 640±140 fs. This dependence is explained by the induced moment of the Pt atom by current flow from the Co layer through the interfaces. The obsd. magnetization dynamics can be attributed to the characteristics of photo-induced Co/Pt thin film phenomena including all-optical switching. (c) 2020 American Institute of Physics.
- 35Moisan, N.; Malinowski, G.; Mauchain, J.; Hehn, M.; Vodungbo, B.; Lüning, J.; Mangin, S.; Fullerton, E. E.; Thiaville, A. Investigating the Role of Superdiffusive Currents in Laser Induced Demagnetization of Ferromagnets with Nanoscale Magnetic Domains. Sci. Rep. 2015, 4, 4658, DOI: 10.1038/srep04658Google ScholarThere is no corresponding record for this reference.
- 36Koopmans, B.; Malinowski, G.; Dalla Longa, F.; Steiauf, D.; Fähnle, M.; Roth, T.; Cinchetti, M.; Aeschlimann, M. Explaining the Paradoxical Diversity of Ultrafast Laser-Induced Demagnetization. Nat. Mater. 2010, 9, 259– 265, DOI: 10.1038/nmat2593Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXitFGlurs%253D&md5=cdc34f24f01922e0a4cc3e26318a146fExplaining the paradoxical diversity of ultrafast laser-induced demagnetizationKoopmans, B.; Malinowski, G.; Dalla Longa, F.; Steiauf, D.; Faehnle, M.; Roth, T.; Cinchetti, M.; Aeschlimann, M.Nature Materials (2010), 9 (3), 259-265CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)Pulsed-laser-induced quenching of ferromagnetic order has intrigued researchers since pioneering works in the 1990s. It is reported that demagnetization in gadolinium proceeds within 100 ps, but three orders of magnitude faster in ferromagnetic transition metals such as nickel. A model based on electron-phonon-mediated spin-flip scattering explains both timescales on equal footing. The authors' interpretation is supported by ab initio ests. of the spin-flip scattering probability, and exptl. fluence dependencies agree perfectly with predictions. A phase diagram is constructed in which two classes of laser-induced magnetization dynamics can be distinguished, where the ratio of the Curie temp. to the at. magnetic moment turns out to have a crucial role. The ultrafast magnetization dynamics can be well described disregarding highly excited electronic states, merely considering the thermalized electron system.
- 37Battiato, M.; Carva, K.; Oppeneer, P. M. Theory of Laser-Induced Ultrafast Superdiffusive Spin Transport in Layered Heterostructures. Phys. Rev. B: Condens. Matter Mater. Phys. 2012, 86, 024404, DOI: 10.1103/PhysRevB.86.024404Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlWgtrzP&md5=2517ab130952b2c592a72d8ee55dd2baTheory of laser-induced ultrafast superdiffusive spin transport in layered heterostructuresBattiato, M.; Carva, K.; Oppeneer, P. M.Physical Review B: Condensed Matter and Materials Physics (2012), 86 (2), 024404/1-024404/16CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)Femtosecond laser excitation of a ferromagnetic material creates energetic spin-polarized electrons that have anomalous transport characteristics. We develop a semiclassical theory that is specifically dedicated to capture the transport of laser-excited nonequil. (NEQ) electrons. The randomly occurring multiple electronic collisions, which give rise to electron thermalization, are treated exactly and we include the generation of electron cascades due to inelastic electron-electron scatterings. The developed theory can, moreover, treat the presence of several different layers in the laser-irradiated material. The derived spin-dependent transport equation is solved numerically and it is shown that the hot NEQ electron spin transport occurs neither in the diffusive nor ballistic regime, it is superdiffusive. As the excited spin majority and minority electrons in typical transition-metal ferromagnets (e.g., Fe, Ni) have distinct, energy-dependent lifetimes, fast spin dynamics in the femtosecond (fs) regime is generated, causing effectively a spin current. As examples, we solve the resulting spin dynamics numerically for typical heterostructures, specifically, a ferromagnetic/nonmagnetic metallic layered junction (i.e., Fe/Al and Ni/Al) and a ferromagnetic/nonmagnetic insulator junction (Fe or Ni layer on a large band-gap insulator as, e.g., MgO). For the ferromagnetic/nonmagnetic metallic junction where the ferromagnetic layer is laser-excited, the computed spin dynamics shows that injection of a superdiffusive spin current in the nonmagnetic layer (A1) is achieved. The injected spin current consists of screened NEQ, mobile majority-spin electrons and is nearly 90% spin-polarized for Ni and about 65% for Fe. Concomitantly, a fast demagnetization of the ferromagnetic polarization in the femtosecond regime is driven. The analogy of the generated spin current to a superdiffusive spin Seebeck effect is surveyed.
- 38Battiato, M.; Carva, K.; Oppeneer, P. M. Superdiffusive Spin Transport as a Mechanism of Ultrafast Demagnetization. Phys. Rev. Lett. 2010, 105, 027203, DOI: 10.1103/PhysRevLett.105.027203Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtVGltbvN&md5=7511580778a030622c9a7bcbaac32761Superdiffusive spin transport as a mechanism of ultrafast demagnetizationBattiato, M.; Carva, K.; Oppeneer, P. M.Physical Review Letters (2010), 105 (2), 027203/1-027203/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)We propose a semiclassical model for femtosecond laser-induced demagnetization due to spin-polarized excited electron diffusion in the superdiffusive regime. Our approach treats the finite elapsed time and transport in space between multiple electronic collisions exactly, as well as the presence of several metal films in the sample. Solving the derived transport equation numerically we show that this mechanism accounts for the exptl. obsd. demagnetization within 200 fs in Ni, without the need to invoke any angular momentum dissipation channel.
- 39Dewhurst, J. K.; Elliott, P.; Shallcross, S.; Gross, E. K. U.; Sharma, S. Laser-Induced Intersite Spin Transfer. Nano Lett. 2018, 18, 1842– 1848, DOI: 10.1021/acs.nanolett.7b05118Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXisFarsLg%253D&md5=7b38e8d9a951f3c5588a25be10b3a3ebLaser-Induced Intersite Spin TransferDewhurst, John Kay; Elliott, Peter; Shallcross, Sam; Gross, Eberhard K. U.; Sharma, SangeetaNano Letters (2018), 18 (3), 1842-1848CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Laser pulses induce spin-selective charge flow that we show to generate dramatic changes in the magnetic structure of materials, including a switching of magnetic order from antiferromagnetic (AFM) to transient ferromagnetic (FM) in multisub-lattice systems. The microscopic mechanism underpinning this ultrafast switching of magnetic order is dominated by spin-selective charge transfer from one magnetic sublattice to another. Because this spin modulation is purely optical in nature (i.e., not mediated indirectly via the spin-orbit interaction) this is one of the fastest means of manipulating spin by light. We further demonstrate this mechanism to be universally applicable to AFM, FM, and ferri-magnets in both multilayer and bulk geometry and provide three rules that encapsulate early-time magnetization dynamics of multisub-lattice systems.
- 40Siegrist, F.; Gessner, J. A.; Ossiander, M.; Denker, C.; Chang, Y.-P.; Schröder, M. C.; Guggenmos, A.; Cui, Y.; Walowski, J.; Martens, U. Light-Wave Dynamic Control of Magnetism. Nature 2019, 571, 240– 244, DOI: 10.1038/s41586-019-1333-xGoogle Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXht1yktL%252FI&md5=2e416b3a81fcb1663bd4da9b33c866e9Light-wave dynamic control of magnetismSiegrist, Florian; Gessner, Julia A.; Ossiander, Marcus; Denker, Christian; Chang, Yi-Ping; Schroeder, Malte C.; Guggenmos, Alexander; Cui, Yang; Walowski, Jakob; Martens, Ulrike; Dewhurst, J. K.; Kleineberg, Ulf; Muenzenberg, Markus; Sharma, Sangeeta; Schultze, MartinNature (London, United Kingdom) (2019), 571 (7764), 240-244CODEN: NATUAS; ISSN:0028-0836. (Nature Research)The enigmatic interplay between electronic and magnetic phenomena obsd. in many early expts. and outlined in Maxwell's equations propelled the development of modern electromagnetism1. Today, the fully controlled evolution of the elec. field of ultrashort laser pulses enables the direct and ultrafast tuning of the electronic properties of matter, which is the cornerstone of light-wave electronics2-7. By contrast, owing to the lack of first-order interaction between light and spin, the magnetic properties of matter can only be affected indirectly and on much longer timescales, through a sequence of optical excitations and subsequent rearrangement of the spin structure8-16. Here we introduce the regime of ultrafast coherent magnetism and show how the magnetic properties of a ferromagnetic layer stack can be manipulated directly by the elec.-field oscillations of light, reducing the magnetic response time to an external stimulus by two orders of magnitude. To track the unfolding dynamics in real time, we develop an attosecond time-resolved magnetic CD detection scheme, revealing optically induced spin and orbital momentum transfer in synchrony with light-field-driven coherent charge relocation17. In tandem with ab initio quantum dynamical modeling, we show how this mechanism enables the simultaneous control of electronic and magnetic properties that are essential for spintronic functionality. Our study unveils light-field coherent control of spin dynamics and macroscopic magnetic moments in the initial non-dissipative temporal regime and establishes optical frequencies as the speed limit of future coherent spintronic applications, spin transistors and data storage media.
- 41Yao, Y. D.; Liou, Y.; Huang, J. C. A.; Liao, S. Y.; Klik, I.; Yang, W. T.; Chang, C. P.; Lo, C. K. Enhancement of Magnetoresistance in Co(1100)/Cr(211) Bilayered Films on MgO(110). J. Appl. Phys. 1996, 79, 6533– 6535, DOI: 10.1063/1.361937Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28Xis1Kmt7s%253D&md5=8b2a3605527825a3a3b6309dceeb1bbfEnhancement of magnetoresistance in Co(1‾100)/Cr(211) bilayered films on MgO(110)Yao, Y. D.; Liou, Y.; Huang, J. C. A.; Liao, S. Y.; Klik, I.; Yang, W. T.; Chang, C. P.; Lo, C. K.Journal of Applied Physics (1996), 79 (8, Pt. 2B), 6533-5CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)The magnetoresistance of epitaxial Co/Cr bilayered films grown on MgO substrates by MBE was studied. The anisotropy magnetoresistance is strongly influenced by the orientation of the Cr buffer.
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References
This article references 41 other publications.
- 1Beaurepaire, E.; Merle, J.-C.; Daunois, A.; Bigot, J.-Y. Ultrafast Spin Dynamics in Ferromagnetic Nickel. Phys. Rev. Lett. 1996, 76, 4250– 4253, DOI: 10.1103/PhysRevLett.76.42501https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XjtFOnsro%253D&md5=b99bac7f843f584d40ffff7077646d8aUltrafast spin dynamics in ferromagnetic nickelBeaurepaire, E.; Merle, J.-C.; Daunois, A.; Bigot, J.-Y.Physical Review Letters (1996), 76 (22), 4250-4253CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)The relaxation processes of electrons and spins systems following the absorption of femtosecond optical pulses in ferromagnetic nickel were studied using optical and magneto-optical pump-probe techniques. The magnetization of the film drops rapidly during he 1st picosecond, but different electron and spin dynamics are obsd. for delays in the range 0-5 ps. The exptl. results are adequately described by a model including three interacting reservoirs (electron, spin, and lattice).
- 2Koopmans, B.; van Kampen, M.; Kohlhepp, J. T.; de Jonge, W. J. M. Ultrafast Magneto-Optics in Nickel: Magnetism or Optics?. Phys. Rev. Lett. 2000, 85, 844– 847, DOI: 10.1103/PhysRevLett.85.8442https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXltVWgs70%253D&md5=792b7c059e44a366980defce24bc2ce4Ultrafast Magneto-Optics in Nickel: Magnetism or Optics?Koopmans, B.; van Kampen, M.; Kohlhepp, J. T.; de Jonge, W. J. M.Physical Review Letters (2000), 85 (4), 844-847CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Several magnetic and optical processes contribute to the magnetooptical response of Ni thin films after excitation by a femtosecond laser pulse. The authors achieved a complete identification by measuring the time-resolved Kerr ellipticity and rotation, as well as its temp. and magnetic field dependence in epitaxially grown (111) and (001) oriented Cu/Ni/Cu wedges. The 1st hundreds of femtosecond the response is dominated by state filling effects. The true demagnetization takes ∼0.5-1 ps. At the longer (sub-ns) time scales the spins precess in their anisotropy field. Simple and transparent models are introduced to substantiate interpretation.
- 3Kirilyuk, A.; Kimel, A. V.; Rasing, T. Ultrafast Optical Manipulation of Magnetic Order. Rev. Mod. Phys. 2010, 82, 2731– 2784, DOI: 10.1103/RevModPhys.82.2731There is no corresponding record for this reference.
- 4Stanciu, C. D.; Tsukamoto, A.; Kimel, A. V.; Hansteen, F.; Kirilyuk, A.; Itoh, A.; Rasing, Th Subpicosecond Magnetization Reversal across Ferrimagnetic Compensation Points. Phys. Rev. Lett. 2007, 99, 217204, DOI: 10.1103/PhysRevLett.99.2172044https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtlGgsb7L&md5=6340000d590a8923ea2fe4698d7ec3c3Subpicosecond Magnetization Reversal across Ferrimagnetic Compensation PointsStanciu, C. D.; Tsukamoto, A.; Kimel, A. V.; Hansteen, F.; Kirilyuk, A.; Itoh, A.; Rasing, Th.Physical Review Letters (2007), 99 (21), 217204/1-217204/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Subpicosecond magnetization reversal is exptl. demonstrated by ultrafast heating of a ferrimagnet across its compensation points, under an applied magnetic field. While the reversal is initiated by crossing the magnetization compensation temp., the short reversal time is related to the angular momentum compensation, where the dynamics of the system is highly accelerated owing to the divergence of the gyromagnetic ratio. These results demonstrate the feasibility of subpicosecond magnetization reversal previously believed impossible.
- 5Ostler, T. A.; Barker, J.; Evans, R. F. L.; Chantrell, R. W.; Atxitia, U.; Chubykalo-Fesenko, O.; El Moussaoui, S.; Le Guyader, L.; Mengotti, E.; Heyderman, L. J. Ultrafast Heating as a Sufficient Stimulus for Magnetization Reversal in a Ferrimagnet. Nat. Commun. 2012, 3, 666, DOI: 10.1038/ncomms16665https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC383htlaquw%253D%253D&md5=71437326fefd4f5f70cc9849e5cd1f2bUltrafast heating as a sufficient stimulus for magnetization reversal in a ferrimagnetOstler T A; Barker J; Evans R F L; Chantrell R W; Atxitia U; Chubykalo-Fesenko O; El Moussaoui S; Le Guyader L; Mengotti E; Heyderman L J; Nolting F; Tsukamoto A; Itoh A; Afanasiev D; Ivanov B A; Kalashnikova A M; Vahaplar K; Mentink J; Kirilyuk A; Rasing Th; Kimel A VNature communications (2012), 3 (), 666 ISSN:.The question of how, and how fast, magnetization can be reversed is a topic of great practical interest for the manipulation and storage of magnetic information. It is generally accepted that magnetization reversal should be driven by a stimulus represented by time-non-invariant vectors such as a magnetic field, spin-polarized electric current, or cross-product of two oscillating electric fields. However, until now it has been generally assumed that heating alone, not represented as a vector at all, cannot result in a deterministic reversal of magnetization, although it may assist this process. Here we show numerically and demonstrate experimentally a novel mechanism of deterministic magnetization reversal in a ferrimagnet driven by an ultrafast heating of the medium resulting from the absorption of a sub-picosecond laser pulse without the presence of a magnetic field.
- 6Alebrand, S.; Gottwald, M.; Hehn, M.; Steil, D.; Cinchetti, M.; Lacour, D.; Fullerton, E. E.; Aeschlimann, M.; Mangin, S. Light-Induced Magnetization Reversal of High-Anisotropy TbCo Alloy Films. Appl. Phys. Lett. 2012, 101, 162408, DOI: 10.1063/1.47591096https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsFCnsbfL&md5=8647bc1b417835c1cf5febb424947e52Light-induced magnetization reversal of high-anisotropy TbCo alloy filmsAlebrand, Sabine; Gottwald, Matthias; Hehn, Michel; Steil, Daniel; Cinchetti, Mirko; Lacour, Daniel; Fullerton, Eric E.; Aeschlimann, Martin; Mangin, StephaneApplied Physics Letters (2012), 101 (16), 162408/1-162408/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Magnetization reversal using circularly polarized light provides a way to control magnetization without any external magnetic field and has the potential to revolutionize magnetic data storage. However, to reach ultra-high d. data storage, high anisotropy media providing thermal stability are needed. Here, we evidence all-optical magnetization switching for different TbxCo1-x ferrimagnetic alloy compns. using fs- and ps-laser pulses and demonstrate all-optical switching for films with anisotropy fields reaching 6 T corresponding to anisotropy consts. of 3 × 106 ergs/cm3. Optical magnetization switching is obsd. only for alloy compns. where the compensation temp. can be reached through sample heating. (c) 2012 American Institute of Physics.
- 7Radu, I.; Vahaplar, K.; Stamm, C.; Kachel, T.; Pontius, N.; Dürr, H. A.; Ostler, T. A.; Barker, J.; Evans, R. F. L.; Chantrell, R. W. Transient Ferromagnetic-like State Mediating Ultrafast Reversal of Antiferromagnetically Coupled Spins. Nature 2011, 472, 205– 208, DOI: 10.1038/nature099017https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXjvFOnt7o%253D&md5=e4cf37e8f1a500275ad5aba0f13d6618Transient ferromagnetic-like state mediating ultrafast reversal of antiferromagnetically coupled spinsRadu, I.; Vahaplar, K.; Stamm, C.; Kachel, T.; Pontius, N.; Duerr, H. A.; Ostler, T. A.; Barker, J.; Evans, R. F. L.; Chantrell, R. W.; Tsukamoto, A.; Itoh, A.; Kirilyuk, A.; Rasing, Th.; Kimel, A. V.Nature (London, United Kingdom) (2011), 472 (7342), 205-208CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)Ferromagnetic or antiferromagnetic spin ordering is governed by the exchange interaction, the strongest force in magnetism. Understanding spin dynamics in magnetic materials is an issue of crucial importance for progress in information processing and recording technol. Usually the dynamics are studied by observing the collective response of exchange-coupled spins, i.e., spin resonances, after an external perturbation by a pulse of magnetic field, current or light. The periods of the corresponding resonances range from one nanosecond for ferromagnets down to one picosecond for antiferromagnets. However, virtually nothing is known about the behavior of spins in a magnetic material after being excited on a timescale faster than that corresponding to the exchange interaction (10-100 fs), i.e., in a non-adiabatic way. Here we use the element-specific technique X-ray magnetic CD to study spin reversal in GdFeCo that is optically excited on a timescale pertinent to the characteristic time of the exchange interaction between Gd and Fe spins. We unexpectedly find that the ultrafast spin reversal in this material, where spins are coupled antiferromagnetically, occurs by way of a transient ferromagnetic-like state. Following the optical excitation, the net magnetizations of the Gd and Fe sublattices rapidly collapse, switch their direction and rebuild their net magnetic moments at substantially different timescales; the net magnetic moment of the Gd sublattice is found to reverse within 1.5 ps, which is substantially slower than the Fe reversal time of 300 fs. Consequently, a transient state characterized by a temporary parallel alignment of the net Gd and Fe moments emerges, despite their ground-state antiferromagnetic coupling. These surprising observations, supported by atomistic simulations, provide a concept for the possibility of manipulating magnetic order on the timescale of the exchange interaction.
- 8Graves, C. E.; Reid, A. H.; Wang, T.; Wu, B.; de Jong, S.; Vahaplar, K.; Radu, I.; Bernstein, D. P.; Messerschmidt, M.; Müller, L. Nanoscale Spin Reversal by Non-Local Angular Momentum Transfer Following Ultrafast Laser Excitation in Ferrimagnetic GdFeCo. Nat. Mater. 2013, 12, 293– 298, DOI: 10.1038/nmat35978https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXktVKmt7Y%253D&md5=5e2ed422686dde48187fd4bec1a6dfa2Nanoscale spin reversal by non-local angular momentum transfer following ultrafast laser excitation in ferrimagnetic GdFeCoGraves, C. E.; Reid, A. H.; Wang, T.; Wu, B.; de Jong, S.; Vahaplar, K.; Radu, I.; Bernstein, D. P.; Messerschmidt, M.; Mueller, L.; Coffee, R.; Bionta, M.; Epp, S. W.; Hartmann, R.; Kimmel, N.; Hauser, G.; Hartmann, A.; Holl, P.; Gorke, H.; Mentink, J. H.; Tsukamoto, A.; Fognini, A.; Turner, J. J.; Schlotter, W. F.; Rolles, D.; Soltau, H.; Strueder, L.; Acremann, Y.; Kimel, A. V.; Kirilyuk, A.; Rasing, Th.; Stoehr, J.; Scherz, A. O.; Duerr, H. A.Nature Materials (2013), 12 (4), 293-298CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)Ultrafast laser techniques have revealed extraordinary spin dynamics in magnetic materials that equil. descriptions of magnetism cannot explain. Particularly important for future applications is understanding non-equil. spin dynamics following laser excitation on the nanoscale, yet the limited spatial resoln. of optical laser techniques has impeded such nanoscale studies. Here we present ultrafast diffraction expts. with an x-ray laser that probes the nanoscale spin dynamics following optical laser excitation in the ferrimagnetic alloy GdFeCo, which exhibits macroscopic all-optical switching. Our study reveals that Gd24Fe66.5Co9.5 displays nanoscale chem. and magnetic inhomogeneities that affect the spin dynamics. In particular, we observe Gd spin reversal in Gd-rich nanoregions within the 1st picosecond driven by the non-local transfer of angular momentum from larger adjacent Fe-rich nanoregions. These results suggest that a magnetic material's microstructure can be engineered to control transient laser-excited spins, potentially allowing faster (∼ 1 ps) spin reversal than in present technologies.
- 9Liu, T.-M.; Wang, T.; Reid, A. H.; Savoini, M.; Wu, X.; Koene, B.; Granitzka, P.; Graves, C. E.; Higley, D. J.; Chen, Z. Nanoscale Confinement of All-Optical Magnetic Switching in TbFeCo - Competition with Nanoscale Heterogeneity. Nano Lett. 2015, 15, 6862– 6868, DOI: 10.1021/acs.nanolett.5b027439https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC287msV2lug%253D%253D&md5=9f03b0bd0721e68492cb2c0ad89e3f2bNanoscale Confinement of All-Optical Magnetic Switching in TbFeCo--Competition with Nanoscale HeterogeneityLiu Tian-Min; Wang Tianhan; Reid Alexander H; Granitzka Patrick; Graves Catherine E; Higley Daniel J; Chen Zhao; Scherz Andreas; Stohr Joachim; Durr Hermann A; Savoini Matteo; Koene Benny; Kimel Alexey V; Kirilyuk Andrei; Rasing Theo; Wu Xiaofei; Razinskas Gary; Hecht Bert; Wu Xiaofei; Granitzka Patrick; Hantschmann Markus; Tsukamoto ArataNano letters (2015), 15 (10), 6862-8 ISSN:.Single femtosecond optical laser pulses, of sufficient intensity, are demonstrated to reverse magnetization in a process known as all-optical switching. Gold two-wire antennas are placed on the all-optical switching film TbFeCo. These structures are resonant with the optical field, and they create a field enhancement in the near-field which confines the area where optical switching can occur. The magnetic switching that occurs around and below the antenna is imaged using resonant X-ray holography and magnetic circular dichroism. The results not only show the feasibility of controllable switching with antenna assistance but also demonstrate the highly inhomogeneous nature of the switching process, which is attributed to the process depending on the material's heterogeneity.
- 10Mangin, S.; Gottwald, M.; Lambert, C.-H.; Steil, D.; Uhlíř, V.; Pang, L.; Hehn, M.; Alebrand, S.; Cinchetti, M.; Malinowski, G. Engineered Materials for All-Optical Helicity-Dependent Magnetic Switching. Nat. Mater. 2014, 13, 286– 292, DOI: 10.1038/nmat386410https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXisFOkurs%253D&md5=ea1789463dff598c75d325fbdfdc6faeEngineered materials for all-optical helicity-dependent magnetic switchingMangin, S.; Gottwald, M.; Lambert, C.-H.; Steil, D.; Uhlir, V.; Pang, L.; Hehn, M.; Alebrand, S.; Cinchetti, M.; Malinowski, G.; Fainman, Y.; Aeschlimann, M.; Fullerton, E. E.Nature Materials (2014), 13 (3), 286-292CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)The possibility of manipulating magnetic systems without applied magnetic fields have attracted growing attention over the past fifteen years. The low-power manipulation of the magnetization, preferably at ultrashort timescales, has become a fundamental challenge with implications for future magnetic information memory and storage technologies. Here the authors explore the optical manipulation of the magnetization in engineered magnetic materials. All-optical helicity-dependent switching (AO-HDS) can be obsd. not only in selected rare earth-transition metal (RE-TM) alloy films but also in a much broader variety of materials, including RE-TM alloys, multilayers and heterostructures. Further RE-free Co-Ir-based synthetic ferrimagnetic heterostructures designed to mimic the magnetic properties of RE-TM alloys also exhibit AO-HDS. These results challenge present theories of AO-HDS and provide a pathway to engineering materials for future applications based on all-optical control of magnetic order.
- 11Lambert, C.-H.; Mangin, S.; Varaprasad, B. S. D. C. S.; Takahashi, Y. K.; Hehn, M.; Cinchetti, M.; Malinowski, G.; Hono, K.; Fainman, Y.; Aeschlimann, M. All-Optical Control of Ferromagnetic Thin Films and Nanostructures. Science 2014, 345, 1337– 1340, DOI: 10.1126/science.125349311https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsV2qtL%252FK&md5=6bca6a08b9677d61de969426f9e820a0All-optical control of ferromagnetic thin films and nanostructuresLambert, C.-H.; Mangin, S.; Varaprasad, B. S. D. Ch. S.; Takahashi, Y. K.; Hehn, M.; Cinchetti, M.; Malinowski, G.; Hono, K.; Fainman, Y.; Aeschlimann, M.; Fullerton, E. E.Science (Washington, DC, United States) (2014), 345 (6202), 1337-1340CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The interplay of light and magnetism allowed light to be used as a probe of magnetic materials. Now the focus has shifted to use polarized light to alter or manipulate magnetism. Here, we demonstrate optical control of ferromagnetic materials ranging from magnetic thin films to multilayers and even granular films being explored for ultra-high-d. magnetic recording. Our finding shows that optical control of magnetic materials is a much more general phenomenon than previously assumed and may have a major impact on data memory and storage industries through the integration of optical control of ferromagnetic bits.
- 12Ellis, M. O. A.; Fullerton, E. E.; Chantrell, R. W. All-Optical Switching in Granular Ferromagnets Caused by Magnetic Circular Dichroism. Sci. Rep. 2016, 6, 30522, DOI: 10.1038/srep3052212https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXksFeltbw%253D&md5=26c5a0068adfa5f807f0ba08fa78b0a9All-optical switching in granular ferromagnets caused by magnetic circular dichroismEllis, Matthew O. A.; Fullerton, Eric E.; Chantrell, Roy W.Scientific Reports (2016), 6 (), 30522CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)Magnetic recording using circularly polarized femtosecond laser pulses is an emerging technol. that would allow write speeds much faster than existing field driven methods. However, the mechanism that drives the magnetization switching in ferromagnets is unclear. Recent theories suggest that the interaction of the light with the magnetized media induces an optomagnetic field within the media, known as the inverse Faraday effect. Here we show that an alternative mechanism, driven by thermal excitation over the anisotropy energy barrier and a difference in the energy absorption depending on polarization, can create a net magnetization over a series of laser pulses in an ensemble of single domain grains. Only a small difference in the absorption is required to reach magnetization levels obsd. exptl. and the model does not preclude the role of the inverse Faraday effect but removes the necessity that the optomagnetic field is 10 s of Tesla in strength.
- 13Kichin, G.; Hehn, M.; Gorchon, J.; Malinowski, G.; Hohlfeld, J.; Mangin, S. From Multiple- to Single-Pulse All-Optical Helicity-Dependent Switching in Ferromagnetic Co/Pt Multilayers. Phys. Rev. Appl. 2019, 12, 024019, DOI: 10.1103/PhysRevApplied.12.02401913https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhvF2jtL7P&md5=3a77f2884bdfb5ecfee5face0860829fFrom Multiple- to Single-Pulse All-Optical Helicity-Dependent Switching in Ferromagnetic Co/Pt MultilayersKichin, G.; Hehn, M.; Gorchon, J.; Malinowski, G.; Hohlfeld, J.; Mangin, S.Physical Review Applied (2019), 12 (2), 024019CODEN: PRAHB2; ISSN:2331-7019. (American Physical Society)All-optical helicity-dependent switching in ferromagnetic Co/Pt multilayers is investigated using magneto-optical microscopy and anomalous Hall effect measurements. A state diagram is built by studying the effect of pulse duration, fluence, and spot size. We use numerical solns. of the three-temp. model to explain that the all-optical helicity-dependent switching mechanism relies on the spin bath reaching temps. close to the Curie point. Further insights into the reversal process are provided by the exptl. demonstration of significant helicity-dependent reversal after a single laser pulse that reveals the involvement of direct angular momentum transfer. Moreover, based on the observation that longer pulse durations and larger spot sizes lead to enhanced reversal efficiency, we identify exptl. conditions that lead to satd. magnetization reversal after just a few tens of laser pulses.
- 14Yamada, K. T.; Kimel, A. V.; Ruta, S.; Chantrell, R.; Prabhakara, K. H.; Li, T.; Ando, F.; Semin, S.; Ono, T.; Kirilyuk, A.; All-Optical Switching of Spins in Ferromagnetic Co/Pt with a Single Dual Pulse. arXiv:1903.01941 2020.There is no corresponding record for this reference.
- 15Vomir, M.; Albrecht, M.; Bigot, J.-Y. Single Shot All Optical Switching of Intrinsic Micron Size Magnetic Domains of a Pt/Co/Pt Ferromagnetic Stack. Appl. Phys. Lett. 2017, 111, 242404, DOI: 10.1063/1.501091515https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvFyjtrfE&md5=a42ef077535a3f3f5648a36dfa921b96Single shot all optical switching of intrinsic micron size magnetic domains of a Pt/Co/Pt ferromagnetic stackVomir, M.; Albrecht, M.; Bigot, J.-Y.Applied Physics Letters (2017), 111 (24), 242404/1-242404/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)We demonstrate that magnetization reversal in a ferromagnetic Pt/Co/Pt stack can be induced by a single femtosecond laser pulse. We find that the size of the switched spot is comparable to the size of the intrinsic magnetic domains. It requires an absorbed energy d. of ∼4 mJ cm-2, beyond which the excited spot fragments into a multidomain structure. The switching process can be toggled with sequential laser pulses and is helicity-independent. Furthermore, the dynamics of the magnetization reversal occurs in a timescale less than one microsecond. These results suggest that all-optical switching in ferromagnetic films requires that the laser spot matches with the specific domain sizes. (c) 2017 American Institute of Physics.
- 16Gorchon, J.; Lambert, C.-H.; Yang, Y.; Pattabi, A.; Wilson, R. B.; Salahuddin, S.; Bokor, J. Single Shot Ultrafast All Optical Magnetization Switching of Ferromagnetic Co/Pt Multilayers. Appl. Phys. Lett. 2017, 111, 042401, DOI: 10.1063/1.499480216https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1WltL7M&md5=47fad5775bd7f94b609c7aa65355a553Single shot ultrafast all optical magnetization switching of ferromagnetic Co/Pt multilayersGorchon, Jon; Lambert, Charles-Henri; Yang, Yang; Pattabi, Akshay; Wilson, Richard B.; Salahuddin, Sayeef; Bokor, JeffreyApplied Physics Letters (2017), 111 (4), 042401/1-042401/5CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)A single femto-second optical pulse can fully reverse the magnetization of a film within picoseconds. Such fast operation hugely increases the range of application of magnetic devices. However, so far, this type of ultrafast switching was restricted to ferri-magnetic GdFeCo films. In contrast, all optical switching of ferro-magnetic films require multiple pulses, thereby being slower and less energy efficient. Here, the authors demonstrate magnetization switching induced by a single laser pulse in various ferromagnetic Co/Pt multilayers grown on GdFeCo, by exploiting the exchange coupling between the two magnetic films. Table-top depth-sensitive time-resolved magneto-optical expts. show that the Co/Pt magnetization switches within 7 ps. This coupling approach will allow ultrafast control of a variety of magnetic films, which is crit. for applications. (c) 2017 American Institute of Physics.
- 17Igarashi, J.; Remy, Q.; Iihama, S.; Malinowski, G.; Hehn, M.; Gorchon, J.; Hohlfeld, J.; Fukami, S.; Ohno, H.; Mangin, S. Engineering Single-Shot All-Optical Switching of Ferromagnetic Materials. Nano Lett. 2020, 20, 8654– 8660, DOI: 10.1021/acs.nanolett.0c0337317https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXitlyrsr3F&md5=5734addb6249c587e45ca0d10f41906eEngineering Single-Shot All-Optical Switching of Ferromagnetic MaterialsIgarashi, Junta; Remy, Quentin; Iihama, Satoshi; Malinowski, Gregory; Hehn, Michel; Gorchon, Jon; Hohlfeld, Julius; Fukami, Shunsuke; Ohno, Hideo; Mangin, StephaneNano Letters (2020), 20 (12), 8654-8660CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Since it was recently demonstrated in a spin-valve structure, magnetization reversal of a ferromagnetic layer using a single ultrashort optical pulse has attracted attention for future ultrafast and energy-efficient magnetic storage or memory devices. However, the mechanism and the role of the magnetic properties of the ferromagnet as well as the time scale of the magnetization switching are not understood. Here, we investigate single-shot all-optical magnetization switching in a GdFeCo/Cu/[CoxNi1-x/Pt] spin-valve structure. We demonstrate that the threshold fluence for switching both the GdFeCo and the ferromagnetic layer depends on the laser pulse duration and the thickness and the Curie temp. of the ferromagnetic layer. CoxNi1-x (x = 0.2, 0.3, 0.4, 0.6, 0.8, 1). We are able to explain most of the exptl. results using a phenomenol. model. This work provides a way to engineer ferromagnetic materials for energy efficient single-shot all-optical magnetization switching.
- 18Cornelissen, T. D.; Córdoba, R.; Koopmans, B. Microscopic Model for All Optical Switching in Ferromagnets. Appl. Phys. Lett. 2016, 108, 142405, DOI: 10.1063/1.494566018https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XlslWltrw%253D&md5=e7efe3c1addaf31097cbb75a2f43de47Microscopic model for all optical switching in ferromagnetsCornelissen, T. D.; Cordoba, R.; Koopmans, B.Applied Physics Letters (2016), 108 (14), 142405/1-142405/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)The microscopic mechanism behind the all optical switching (AOS) in ferromagnets has triggered intense scientific debate. Here, the microscopic three-temp. model is utilized to describe AOS in a perpendicularly magnetized ferromagnetic Co/Pt system. We demonstrate that AOS in such a ferromagnet can be explained with the Inverse Faraday Effect (IFE). The influence of the strength and lifetime of the IFE induced field pulse on the switching process are investigated. We found that because of strong spin-orbit coupling, the minimal lifetime of the IFE needed to obtain switching is of the order of 0.1 ps, which is shorter than previously assumed. Moreover, spatial images of the domain pattern after AOS in Co/Pt, as well as their dependence on applying an opposite magnetic field, are qual. reproduced. (c) 2016 American Institute of Physics.
- 19Yamamoto, K.; Kubota, Y.; Suzuki, M.; Hirata, Y.; Carva, K.; Berritta, M.; Takubo, K.; Uemura, Y.; Fukaya, R.; Tanaka, K. Ultrafast Demagnetization of Pt Magnetic Moment in L10-FePt Probed by Magnetic Circular Dichroism at a Hard x-Ray Free Electron Laser. New J. Phys. 2019, 21, 123010, DOI: 10.1088/1367-2630/ab5ac219https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhs1yiurbK&md5=80e45e0e104cfb68f83e819087c5215dUltrafast demagnetization of Pt magnetic moment in L10-FePt probed by magnetic circular dichroism at a hard x-ray free electron laserYamamoto, Kohei; Kubota, Yuya; Suzuki, Motohiro; Hirata, Yasuyuki; Carva, Karel; Berritta, Marco; Takubo, Kou; Uemura, Yohei; Fukaya, Ryo; Tanaka, Kenta; Nishimura, Wataru; Ohkochi, Takuo; Katayama, Tetsuo; Togashi, Tadashi; Tamasaku, Kenji; Yabashi, Makina; Tanaka, Yoshihito; Seki, Takeshi; Takanashi, Koki; Oppeneer, Peter M.; Wadati, HirokiNew Journal of Physics (2019), 21 (Dec.), 123010CODEN: NJOPFM; ISSN:1367-2630. (IOP Publishing Ltd.)Unraveling the origin of ultrafast demagnetization in multisublattice ferromagnetic materials requires femtosecond x-ray techniques to trace the magnetic moment dynamics on individual elements, but this could not yet be achieved in the hard x-ray regime.Wedemonstrate here the first ultrafast demagnetization dynamics in the ferromagnetic heavy 5d-transition metal Pt using circularlypolarized hard x-rays at an x-ray free electron laser (XFEL). The decay time of laser-induced demagnetization of L10-FePt is detd. to be τPt = 0.61 ± 0.04 ps using time-resolved x-ray magnetic CD at the PtL3 edge, whereas magneto-optical Kerr measurements indicate the decay time for the totalmagnetization as τtotal < 0.1 ps. A transientmagnetic statewith a photo-modulated ratio of the 3d and 5d magnetic moments is demonstrated for pump-probe delays larger than 1 ps. We explain this distinct photo-modulated transient magnetic state by the induced-moment behavior of the Pt atom and the x-ray probing depth. Our findings pave the way for the future use of XFELs to disentangle at. spin dynamics contributions.
- 20Hofherr, M.; Moretti, S.; Shim, J.; Häuser, S.; Safonova, N. Y.; Stiehl, M.; Ali, A.; Sakshath, S.; Kim, J. W.; Kim, D. H. Induced versus Intrinsic Magnetic Moments in Ultrafast Magnetization Dynamics. Phys. Rev. B: Condens. Matter Mater. Phys. 2018, 98, 174419, DOI: 10.1103/PhysRevB.98.174419There is no corresponding record for this reference.
- 21Kuiper, K. C.; Roth, T.; Schellekens, A. J.; Schmitt, O.; Koopmans, B.; Cinchetti, M.; Aeschlimann, M. Spin-Orbit Enhanced Demagnetization Rate in Co/Pt-Multilayers. Appl. Phys. Lett. 2014, 105, 202402, DOI: 10.1063/1.490206921https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhvFKktrjN&md5=40845ad6285c3be2486baad90f3325e0Spin-orbit enhanced demagnetization rate in Co/Pt-multilayersKuiper, K. C.; Roth, T.; Schellekens, A. J.; Schmitt, O.; Koopmans, B.; Cinchetti, M.; Aeschlimann, M.Applied Physics Letters (2014), 105 (20), 202402/1-202402/4CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)In order to explore the role of enhanced spin-orbit interactions on the laser-induced ultrafast magnetization dynamics, we performed a comparative study on Co thin films and Co/Pt multilayers. We show that the presence of the Co/Pt interfaces gives rise to a 3-fold faster demagnetization upon femtosecond laser heating. Exptl. data for a wide range of laser fluences are analyzed using the microscopic 3-temp. model. We find that the Elliott-Yafet spin-flip scattering in the multilayer structure is increased by at least a factor of four with respect to the elementary Co film. (c) 2014 American Institute of Physics.
- 22Hecker, M.; Oppeneer, P. M.; Valencia, S.; Mertins, H.-Ch.; Schneider, C. M. Soft X-Ray Magnetic Reflection Spectroscopy at the 3p Absorption Edges of Thin Fe Films. J. Electron Spectrosc. Relat. Phenom. 2005, 144–147, 881– 884, DOI: 10.1016/j.elspec.2005.01.15122https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXjsVymt7g%253D&md5=de8d6b1366d4e0d5e502217fcf589ff3Soft X-ray magnetic reflection spectroscopy at the 3p absorption edges of thin Fe filmsHecker, M.; Oppeneer, P. M.; Valencia, S.; Mertins, H.-Ch.; Schneider, C. M.Journal of Electron Spectroscopy and Related Phenomena (2005), 144-147 (), 881-884CODEN: JESRAW; ISSN:0368-2048. (Elsevier B.V.)Soft X-ray magnetic reflection spectroscopy with linearly polarized light was used to investigate thin Fe films close to their 3p absorption edges. The high reflectivity in this spectral range enables one to measure magnetic signals in a wide angular range up to near-normal incidence. A strong amplification of the T-MOKE (transversal magneto-optical Kerr effect) asymmetry ratio occurs close to scattering angles of θ ∼ 45° and leads to huge magnetic signals of more than 50%. Utilizing these high signals, the course of the in-plane sample magnetization during the hysteresis cycle was detd. from the variation of the hysteresis loops with the measurement geometry.
- 23Willems, F.; von Korff Schmising, C.; Strüber, C.; Schick, D.; Engel, D. W.; Dewhurst, J. K.; Elliott, P.; Sharma, S.; Eisebitt, S. Optical Inter-Site Spin Transfer Probed by Energy and Spin-Resolved Transient Absorption Spectroscopy. Nat. Commun. 2020, 11, 871, DOI: 10.1038/s41467-020-14691-523https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXkvFajtbo%253D&md5=f62879c503d177cd1f129699a29b53f1Optical inter-site spin transfer probed by energy and spin-resolved transient absorption spectroscopyWillems, Felix; von Korff Schmising, Clemens; Strueber, Christian; Schick, Daniel; Engel, Dieter W.; Dewhurst, J. K.; Elliott, Peter; Sharma, Sangeeta; Eisebitt, StefanNature Communications (2020), 11 (1), 871CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)Abstr.: Optically driven spin transport is the fastest and most efficient process to manipulate macroscopic magnetization as it does not rely on secondary mechanisms to dissipate angular momentum. In the present work, we show that such an optical inter-site spin transfer (OISTR) from Pt to Co emerges as a dominant mechanism governing the ultrafast magnetization dynamics of a CoPt alloy. To demonstrate this, we perform a joint theor. and exptl. investigation to det. the transient changes of the helicity dependent absorption in the extreme UV spectral range. We show that the helicity dependent absorption is directly related to changes of the transient spin-split d. of states, allowing us to link the origin of OISTR to the available minority states above the Fermi level. This makes OISTR a general phenomenon in optical manipulation of multi-component magnetic systems.
- 24Plogmaker, S.; Terschlüsen, J. A.; Krebs, N.; Svanqvist, M.; Forsberg, J.; Cappel, U. B.; Rubensson, J.-E.; Siegbahn, H.; Söderström, J. HELIOS—A Laboratory Based on High-Order Harmonic Generation of Extreme Ultraviolet Photons for Time-Resolved Spectroscopy. Rev. Sci. Instrum. 2015, 86, 123107, DOI: 10.1063/1.493746324https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitVKjtLbL&md5=e7b0980a3b75e46eeed6c78be3548ae7HELIOS - A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopyPlogmaker, S.; Terschlusen, J. A.; Krebs, N.; Svanqvist, M.; Forsberg, J.; Cappel, U. B.; Rubensson, J.-E.; Siegbahn, H.; Soederstroem, J.Review of Scientific Instruments (2015), 86 (12), 123107/1-123107/9CODEN: RSINAK; ISSN:0034-6748. (American Institute of Physics)The HELIOS (High Energy Laser Induced Overtone Source) lab., an inhouse high-order harmonic generation facility which generates extreme UV (XUV) photon pulses at 15-70 eV with monochromatized XUV pulse lengths <35 fs, is presented. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe expts. with wavelengths ranging from 240 nm to 20,000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, 1st monochromatized spectra are shown with an intensity of 2 × 1010 photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is <25 fs after monochromatization. (c) 2015 American Institute of Physics.
- 25Stefanuik, R.; Knut, R.; Jana, S.; Terschlüsen, J. A.; Sandell, A.; Söderström, J. Developments and Enhancements to the HELIOS Pump Probe System. J. Electron Spectrosc. Relat. Phenom. 2018, 224, 33– 37, DOI: 10.1016/j.elspec.2017.09.00425https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsFCqs7rE&md5=ed1d38a79c595528783e0e81d228a9a4Developments and enhancements to the HELIOS pump probe systemStefanuik, R.; Knut, R.; Jana, S.; Terschlusen, J. A.; Sandell, A.; Soederstroem, J.Journal of Electron Spectroscopy and Related Phenomena (2018), 224 (), 33-37CODEN: JESRAW; ISSN:0368-2048. (Elsevier B.V.)In this progress report we describe several design improvements that have been implemented at the HELIOS lab., as well as presenting the output characteristics that have been measured as a result. The main focus will be on the redesign of the gas cell, which has enhanced the photon flux of the XUV probe beam. Also, a frequency trippler utilizing sum frequency generation has been installed at the end of the pump line, which increases the photon flux available for both 3.1 eV (400 nm) and 4.66 eV (266 nm) applications without significant increment in the pulse width of the pump.
- 26Jana, S.; Terschlüsen, J. A.; Stefanuik, R.; Plogmaker, S.; Troisi, S.; Malik, R. S.; Svanqvist, M.; Knut, R.; Söderström, J.; Karis, O. A Setup for Element Specific Magnetization Dynamics Using the Transverse Magneto-Optic Kerr Effect in the Energy Range of 30–72 EV. Rev. Sci. Instrum. 2017, 88, 033113, DOI: 10.1063/1.497890726https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXltlKku7s%253D&md5=753607eba9473ed8e18736eac2fe50aeA setup for element specific magnetization dynamics using the transverse magneto-optic Kerr effect in the energy range of 30-72 eVJana, S.; Terschlusen, J. A.; Stefanuik, R.; Plogmaker, S.; Troisi, S.; Malik, R. S.; Svanqvist, M.; Knut, R.; Soederstroem, J.; Karis, O.Review of Scientific Instruments (2017), 88 (3), 033113/1-033113/8CODEN: RSINAK; ISSN:0034-6748. (American Institute of Physics)In this paper, we present a spectrometer that is designed for element-specific and time-resolved transverse magneto-optic Kerr effect expts. at the high-harmonic generation pump-probe facility High Energy Laser Induced Overtone Source (HELIOS) lab. HELIOS delivers photons with energies between 30 eV and 72 eV with an overall time resoln. of less than 40 fs. The spectrometer is based on a Rowland-circle geometry and allows for simultaneous measurements of all magnetic transition-metal elements. The setup also features easy sample transfer and alignment, and it combines high photon throughput, optimized data acquisition, and a fast switching of the magnetic field at the sample. The spectrometer performance is demonstrated by measuring the ultrafast demagnetization of permalloy. Our data are, for all practical purposes, identical to what have been reported in the earlier high-order harmonic generation work of a similar sample by Mathias et al. [Proc. Natl. Acad. Sci. U. S. A. 109, 4792-4797 (2012)], however, obtained within 15% of the acquisition time compared to their study. Furthermore, our data show a shift of the demagnetization curve of Ni relative to Fe, which has previously been interpreted as a delay of the Ni demagnetization to that of Fe [S. Mathias et al., Proc. Natl. Acad. Sci. U. S. A. 109, 4792-4797 (2012)]. (c) 2017 American Institute of Physics.
- 27Blaha, P.; Schwarz, K.; Madsen, G.; Kvasnicka, D.; Luitz, J. WIEN2k: An Augmented Plane Wave plus Local Orbitals Program for Calculating Crystal Properties; Technische Universität Wien: Vienna, Austria, 2001.There is no corresponding record for this reference.
- 28Valencia, S.; Kleibert, A.; Gaupp, A.; Rusz, J.; Legut, D.; Bansmann, J.; Gudat, W.; Oppeneer, P. M. Quadratic X-Ray Magneto-Optical Effect upon Reflection in a Near-Normal-Incidence Configuration at the M Edges of 3d-Transition Metals. Phys. Rev. Lett. 2010, 104, 187401, DOI: 10.1103/PhysRevLett.104.18740128https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXmslKmtbw%253D&md5=08a857aaea9718f3b7ab18973670ddbdQuadratic X-ray magneto-optical effect upon reflection in a near-normal-incidence configuration at the M edges of 3d-transition metalsValencia, S.; Kleibert, A.; Gaupp, A.; Rusz, J.; Legut, D.; Bansmann, J.; Gudat, W.; Oppeneer, P. M.Physical Review Letters (2010), 104 (18), 187401/1-187401/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)The authors obsd. a quadratic x-ray magneto-optical effect in near-normal-incidence reflection at the M edges of Fe. The effect appears as the magnetically induced rotation of ∼0.1° of the polarization plane of linearly polarized x-ray radiation upon reflection. A comparison of the measured rotation spectrum with results from x-ray magnetic linear dichroism data demonstrates that this is the 1st observation of the Schaefer-Hubert effect in the x-ray regime. Ab initio d.-functional theory calcns. reveal that hybridization effects of the 3p core states necessarily need to be considered when interpreting exptl. data. The discovered magneto-x-ray effect holds promise for future ultrafast and element-selective studies of ferromagnetic as well as antiferromagnetic materials.
- 29Turek, I.; Drchal, V.; Kudrnovsky, J.; Sob, M.; Weinberger, P. Electronic Structure of Disordered Alloys, Surfaces and Interfaces; Springer: Boston, MA, 1997.There is no corresponding record for this reference.
- 30Staunton, J.; Gyorffy, B. L.; Pindor, A. J.; Stocks, G. M.; Winter, H. Electronic Structure of Metallic Ferromagnets above the Curie Temperature. J. Phys. F: Met. Phys. 1985, 15, 1387, DOI: 10.1088/0305-4608/15/6/01930https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2MXktFGksLY%253D&md5=afcd21ab6ff9ab510f710c8bb6b866c7Electronic structure of metallic ferromagnets above the Curie temperatureStaunton, J.; Gyorffy, B. L.; Pindor, A. J.; Stocks, G. M.; Winter, H.Journal of Physics F: Metal Physics (1985), 15 (6), 1387-404CODEN: JPFMAT; ISSN:0305-4608.The electronic structure of Fe and Ni above their Curie temps. in their disordered local moment (DLM) states is described as a function of wavevector k and energy ε. The Bloch spectral function, ‾A(k, ε), averaged over the orientational configurations of the local moments, is calcd. at selected points in the Brillouin zone and the shape and smearing of the "Fermi surface" is detd. Bcc. Fe, with a local moment of 1.9 μB, can show an exchange splitting at some points, while in other regions of the Brillouin zone no such splitting occurs. For comparison fcc. Fe, which also supports a substantial local moment, is also studied. It has similar features, but the smearing of the "bands" is more pronounced. On the other hand, the electronic structure of Ni is quite different; it shows no such local exchange splitting, but is able to support a small local moment of 0.2 μB. The resulting picture for the electronic structure of Ni is that of a paramagnetic smeared "Stoner-Wohlfarth" model.
- 31Wagenknecht, D.; Šmejkal, L.; Kašpar, Z.; Sinova, J.; Jungwirth, T.; Kudrnovský, J.; Carva, K.; Turek, I. Temperature-Dependent Resistivity and Anomalous Hall Effect in NiMnSb from First Principles. Phys. Rev. B: Condens. Matter Mater. Phys. 2019, 99, 174433, DOI: 10.1103/PhysRevB.99.174433There is no corresponding record for this reference.
- 32Shishidou, T.; Imada, S.; Muro, T.; Oda, F.; Kimura, A.; Suga, S.; Miyahara, T.; Kanomata, T.; Kaneko, T. Strong Fano Effect in the Magnetic Circular Dichroism of the Pt N6,7 Core Absorption of Ferromagnetic CoPt3. Phys. Rev. B: Condens. Matter Mater. Phys. 1997, 55, 3749– 3756, DOI: 10.1103/PhysRevB.55.3749There is no corresponding record for this reference.
- 33Willems, F.; Smeenk, C. T. L.; Zhavoronkov, N.; Kornilov, O.; Radu, I.; Schmidbauer, M.; Hanke, M.; von Korff Schmising, C.; Vrakking, M. J. J.; Eisebitt, S. Probing Ultrafast Spin Dynamics with High-Harmonic Magnetic Circular Dichroism Spectroscopy. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 92, 220405, DOI: 10.1103/PhysRevB.92.22040533https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XkvVWhsrs%253D&md5=32fd089d1a4f9f8727b5c35f0176049bProbing ultrafast spin dynamics with high-harmonic magnetic circular dichroism spectroscopyWillems, F.; Smeenk, C. T. L.; Zhavoronkov, N.; Kornilov, O.; Radu, I.; Schmidbauer, M.; Hanke, M.; von Korff Schmising, C.; Vrakking, M. J. J.; Eisebitt, S.Physical Review B: Condensed Matter and Materials Physics (2015), 92 (22), 220405/1-220405/5CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)Magnetic CD in the extreme UV (XUV) spectral range is a powerful technique for element-specific probing of magnetization in multicomponent magnetic alloys and multilayers. We combine a high-harmonic generation source with a λ/4 phase shifter to obtain circularly polarized XUV femtosecond pulses for ultrafast magnetization studies. We report on simultaneously measured resonant magnetic CD (MCD) of Co and Ni at their resp. M2,3 edges and of Pt at its O edge, originating from interface magnetism. We present a time-resolved MCD absorption measurement of a thin magnetic Pt/Co/Pt film, showing simultaneous demagnetization of Co and Pt on a femtosecond time scale.
- 34Yamamoto, K.; Moussaoui, S. E.; Hirata, Y.; Yamamoto, S.; Kubota, Y.; Owada, S.; Yabashi, M.; Seki, T.; Takanashi, K.; Matsuda, I. Element-Selectively Tracking Ultrafast Demagnetization Process in Co/Pt Multilayer Thin Films by the Resonant Magneto-Optical Kerr Effect. Appl. Phys. Lett. 2020, 116, 172406, DOI: 10.1063/5.000539334https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXosVylsLo%253D&md5=598ccaae0f43556419b57375fe9f7bb4Element-selectively tracking ultrafast demagnetization process in Co/Pt multilayer thin films by the resonant magneto-optical Kerr effectYamamoto, Kohei; Moussaoui, Souliman El; Hirata, Yasuyuki; Yamamoto, Susumu; Kubota, Yuya; Owada, Shigeki; Yabashi, Makina; Seki, Takeshi; Takanashi, Koki; Matsuda, Iwao; Wadati, HirokiApplied Physics Letters (2020), 116 (17), 172406/1-172406/5CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)We examd. the photo-induced dynamics of ferromagnetic Co/Pt thin films exhibiting perpendicular magnetic anisotropy by means of the resonant polar magneto-optical Kerr effect with element specificity. The investigation was conducted at Pt N6,7 and Co M2,3 edges using an x-ray free electron laser. The obtained results showed a clear element dependence of photo-induced demagnetization time scales: τCodemag. = 80±60 fs and τPtdemag. = 640±140 fs. This dependence is explained by the induced moment of the Pt atom by current flow from the Co layer through the interfaces. The obsd. magnetization dynamics can be attributed to the characteristics of photo-induced Co/Pt thin film phenomena including all-optical switching. (c) 2020 American Institute of Physics.
- 35Moisan, N.; Malinowski, G.; Mauchain, J.; Hehn, M.; Vodungbo, B.; Lüning, J.; Mangin, S.; Fullerton, E. E.; Thiaville, A. Investigating the Role of Superdiffusive Currents in Laser Induced Demagnetization of Ferromagnets with Nanoscale Magnetic Domains. Sci. Rep. 2015, 4, 4658, DOI: 10.1038/srep04658There is no corresponding record for this reference.
- 36Koopmans, B.; Malinowski, G.; Dalla Longa, F.; Steiauf, D.; Fähnle, M.; Roth, T.; Cinchetti, M.; Aeschlimann, M. Explaining the Paradoxical Diversity of Ultrafast Laser-Induced Demagnetization. Nat. Mater. 2010, 9, 259– 265, DOI: 10.1038/nmat259336https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXitFGlurs%253D&md5=cdc34f24f01922e0a4cc3e26318a146fExplaining the paradoxical diversity of ultrafast laser-induced demagnetizationKoopmans, B.; Malinowski, G.; Dalla Longa, F.; Steiauf, D.; Faehnle, M.; Roth, T.; Cinchetti, M.; Aeschlimann, M.Nature Materials (2010), 9 (3), 259-265CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)Pulsed-laser-induced quenching of ferromagnetic order has intrigued researchers since pioneering works in the 1990s. It is reported that demagnetization in gadolinium proceeds within 100 ps, but three orders of magnitude faster in ferromagnetic transition metals such as nickel. A model based on electron-phonon-mediated spin-flip scattering explains both timescales on equal footing. The authors' interpretation is supported by ab initio ests. of the spin-flip scattering probability, and exptl. fluence dependencies agree perfectly with predictions. A phase diagram is constructed in which two classes of laser-induced magnetization dynamics can be distinguished, where the ratio of the Curie temp. to the at. magnetic moment turns out to have a crucial role. The ultrafast magnetization dynamics can be well described disregarding highly excited electronic states, merely considering the thermalized electron system.
- 37Battiato, M.; Carva, K.; Oppeneer, P. M. Theory of Laser-Induced Ultrafast Superdiffusive Spin Transport in Layered Heterostructures. Phys. Rev. B: Condens. Matter Mater. Phys. 2012, 86, 024404, DOI: 10.1103/PhysRevB.86.02440437https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlWgtrzP&md5=2517ab130952b2c592a72d8ee55dd2baTheory of laser-induced ultrafast superdiffusive spin transport in layered heterostructuresBattiato, M.; Carva, K.; Oppeneer, P. M.Physical Review B: Condensed Matter and Materials Physics (2012), 86 (2), 024404/1-024404/16CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)Femtosecond laser excitation of a ferromagnetic material creates energetic spin-polarized electrons that have anomalous transport characteristics. We develop a semiclassical theory that is specifically dedicated to capture the transport of laser-excited nonequil. (NEQ) electrons. The randomly occurring multiple electronic collisions, which give rise to electron thermalization, are treated exactly and we include the generation of electron cascades due to inelastic electron-electron scatterings. The developed theory can, moreover, treat the presence of several different layers in the laser-irradiated material. The derived spin-dependent transport equation is solved numerically and it is shown that the hot NEQ electron spin transport occurs neither in the diffusive nor ballistic regime, it is superdiffusive. As the excited spin majority and minority electrons in typical transition-metal ferromagnets (e.g., Fe, Ni) have distinct, energy-dependent lifetimes, fast spin dynamics in the femtosecond (fs) regime is generated, causing effectively a spin current. As examples, we solve the resulting spin dynamics numerically for typical heterostructures, specifically, a ferromagnetic/nonmagnetic metallic layered junction (i.e., Fe/Al and Ni/Al) and a ferromagnetic/nonmagnetic insulator junction (Fe or Ni layer on a large band-gap insulator as, e.g., MgO). For the ferromagnetic/nonmagnetic metallic junction where the ferromagnetic layer is laser-excited, the computed spin dynamics shows that injection of a superdiffusive spin current in the nonmagnetic layer (A1) is achieved. The injected spin current consists of screened NEQ, mobile majority-spin electrons and is nearly 90% spin-polarized for Ni and about 65% for Fe. Concomitantly, a fast demagnetization of the ferromagnetic polarization in the femtosecond regime is driven. The analogy of the generated spin current to a superdiffusive spin Seebeck effect is surveyed.
- 38Battiato, M.; Carva, K.; Oppeneer, P. M. Superdiffusive Spin Transport as a Mechanism of Ultrafast Demagnetization. Phys. Rev. Lett. 2010, 105, 027203, DOI: 10.1103/PhysRevLett.105.02720338https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtVGltbvN&md5=7511580778a030622c9a7bcbaac32761Superdiffusive spin transport as a mechanism of ultrafast demagnetizationBattiato, M.; Carva, K.; Oppeneer, P. M.Physical Review Letters (2010), 105 (2), 027203/1-027203/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)We propose a semiclassical model for femtosecond laser-induced demagnetization due to spin-polarized excited electron diffusion in the superdiffusive regime. Our approach treats the finite elapsed time and transport in space between multiple electronic collisions exactly, as well as the presence of several metal films in the sample. Solving the derived transport equation numerically we show that this mechanism accounts for the exptl. obsd. demagnetization within 200 fs in Ni, without the need to invoke any angular momentum dissipation channel.
- 39Dewhurst, J. K.; Elliott, P.; Shallcross, S.; Gross, E. K. U.; Sharma, S. Laser-Induced Intersite Spin Transfer. Nano Lett. 2018, 18, 1842– 1848, DOI: 10.1021/acs.nanolett.7b0511839https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXisFarsLg%253D&md5=7b38e8d9a951f3c5588a25be10b3a3ebLaser-Induced Intersite Spin TransferDewhurst, John Kay; Elliott, Peter; Shallcross, Sam; Gross, Eberhard K. U.; Sharma, SangeetaNano Letters (2018), 18 (3), 1842-1848CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)Laser pulses induce spin-selective charge flow that we show to generate dramatic changes in the magnetic structure of materials, including a switching of magnetic order from antiferromagnetic (AFM) to transient ferromagnetic (FM) in multisub-lattice systems. The microscopic mechanism underpinning this ultrafast switching of magnetic order is dominated by spin-selective charge transfer from one magnetic sublattice to another. Because this spin modulation is purely optical in nature (i.e., not mediated indirectly via the spin-orbit interaction) this is one of the fastest means of manipulating spin by light. We further demonstrate this mechanism to be universally applicable to AFM, FM, and ferri-magnets in both multilayer and bulk geometry and provide three rules that encapsulate early-time magnetization dynamics of multisub-lattice systems.
- 40Siegrist, F.; Gessner, J. A.; Ossiander, M.; Denker, C.; Chang, Y.-P.; Schröder, M. C.; Guggenmos, A.; Cui, Y.; Walowski, J.; Martens, U. Light-Wave Dynamic Control of Magnetism. Nature 2019, 571, 240– 244, DOI: 10.1038/s41586-019-1333-x40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXht1yktL%252FI&md5=2e416b3a81fcb1663bd4da9b33c866e9Light-wave dynamic control of magnetismSiegrist, Florian; Gessner, Julia A.; Ossiander, Marcus; Denker, Christian; Chang, Yi-Ping; Schroeder, Malte C.; Guggenmos, Alexander; Cui, Yang; Walowski, Jakob; Martens, Ulrike; Dewhurst, J. K.; Kleineberg, Ulf; Muenzenberg, Markus; Sharma, Sangeeta; Schultze, MartinNature (London, United Kingdom) (2019), 571 (7764), 240-244CODEN: NATUAS; ISSN:0028-0836. (Nature Research)The enigmatic interplay between electronic and magnetic phenomena obsd. in many early expts. and outlined in Maxwell's equations propelled the development of modern electromagnetism1. Today, the fully controlled evolution of the elec. field of ultrashort laser pulses enables the direct and ultrafast tuning of the electronic properties of matter, which is the cornerstone of light-wave electronics2-7. By contrast, owing to the lack of first-order interaction between light and spin, the magnetic properties of matter can only be affected indirectly and on much longer timescales, through a sequence of optical excitations and subsequent rearrangement of the spin structure8-16. Here we introduce the regime of ultrafast coherent magnetism and show how the magnetic properties of a ferromagnetic layer stack can be manipulated directly by the elec.-field oscillations of light, reducing the magnetic response time to an external stimulus by two orders of magnitude. To track the unfolding dynamics in real time, we develop an attosecond time-resolved magnetic CD detection scheme, revealing optically induced spin and orbital momentum transfer in synchrony with light-field-driven coherent charge relocation17. In tandem with ab initio quantum dynamical modeling, we show how this mechanism enables the simultaneous control of electronic and magnetic properties that are essential for spintronic functionality. Our study unveils light-field coherent control of spin dynamics and macroscopic magnetic moments in the initial non-dissipative temporal regime and establishes optical frequencies as the speed limit of future coherent spintronic applications, spin transistors and data storage media.
- 41Yao, Y. D.; Liou, Y.; Huang, J. C. A.; Liao, S. Y.; Klik, I.; Yang, W. T.; Chang, C. P.; Lo, C. K. Enhancement of Magnetoresistance in Co(1100)/Cr(211) Bilayered Films on MgO(110). J. Appl. Phys. 1996, 79, 6533– 6535, DOI: 10.1063/1.36193741https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28Xis1Kmt7s%253D&md5=8b2a3605527825a3a3b6309dceeb1bbfEnhancement of magnetoresistance in Co(1‾100)/Cr(211) bilayered films on MgO(110)Yao, Y. D.; Liou, Y.; Huang, J. C. A.; Liao, S. Y.; Klik, I.; Yang, W. T.; Chang, C. P.; Lo, C. K.Journal of Applied Physics (1996), 79 (8, Pt. 2B), 6533-5CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)The magnetoresistance of epitaxial Co/Cr bilayered films grown on MgO substrates by MBE was studied. The anisotropy magnetoresistance is strongly influenced by the orientation of the Cr buffer.