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Determination of sub-ps lattice dynamics in FeRh thin films. Sci Rep 2022; 12:8584. [PMID: 35595862 PMCID: PMC9122986 DOI: 10.1038/s41598-022-12602-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 05/12/2022] [Indexed: 11/08/2022] Open
Abstract
Understanding the ultrashort time scale structural dynamics of the FeRh metamagnetic phase transition is a key element in developing a complete explanation of the mechanism driving the evolution from an antiferromagnetic to ferromagnetic state. Using an X-ray free electron laser we determine, with sub-ps time resolution, the time evolution of the (-101) lattice diffraction peak following excitation using a 35 fs laser pulse. The dynamics at higher laser fluence indicates the existence of a transient lattice state distinct from the high temperature ferromagnetic phase. By extracting the lattice temperature and comparing it with values obtained in a quasi-static diffraction measurement, we estimate the electron-phonon coupling in FeRh thin films as a function of laser excitation fluence. A model is presented which demonstrates that the transient state is paramagnetic and can be reached by a subset of the phonon bands. A complete description of the FeRh structural dynamics requires consideration of coupling strength variation across the phonon frequencies.
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Seifert TS, Martens U, Radu F, Ribow M, Berritta M, Nádvorník L, Starke R, Jungwirth T, Wolf M, Radu I, Münzenberg M, Oppeneer PM, Woltersdorf G, Kampfrath T. Frequency-Independent Terahertz Anomalous Hall Effect in DyCo 5 , Co 32 Fe 68 , and Gd 27 Fe 73 Thin Films from DC to 40 THz. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2007398. [PMID: 33656190 DOI: 10.1002/adma.202007398] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 12/21/2020] [Indexed: 06/12/2023]
Abstract
The anomalous Hall effect (AHE) is a fundamental spintronic charge-to-charge-current conversion phenomenon and closely related to spin-to-charge-current conversion by the spin Hall effect. Future high-speed spintronic devices will crucially rely on such conversion phenomena at terahertz (THz) frequencies. Here, it is revealed that the AHE remains operative from DC up to 40 THz with a flat frequency response in thin films of three technologically relevant magnetic materials: DyCo5 , Co32 Fe68 , and Gd27 Fe73 . The frequency-dependent conductivity-tensor elements σxx and σyx are measured, and good agreement with DC measurements is found. The experimental findings are fully consistent with ab initio calculations of σyx for CoFe and highlight the role of the large Drude scattering rate (≈100 THz) of metal thin films, which smears out any sharp spectral features of the THz AHE. Finally, it is found that the intrinsic contribution to the THz AHE dominates over the extrinsic mechanisms for the Co32 Fe68 sample. The results imply that the AHE and related effects such as the spin Hall effect are highly promising ingredients of future THz spintronic devices reliably operating from DC to 40 THz and beyond.
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Affiliation(s)
- Tom S Seifert
- Department of Physics, Freie Universität Berlin, Berlin, 14195, Germany
- Department of Physical Chemistry, Fritz-Haber-Institute of the Max-Planck-Society, Berlin, 14195, Germany
| | - Ulrike Martens
- Institute of Physics, University of Greifswald, Greifswald, 17489, Germany
| | - Florin Radu
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, Berlin, 12489, Germany
| | - Mirkow Ribow
- Institute of Physics, Martin-Luther Universität Halle-Wittenberg, Halle (Saale), 06120, Germany
| | - Marco Berritta
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, Uppsala, SE-75120, Sweden
| | - Lukáš Nádvorník
- Faculty of Mathematics and Physics, Charles University, Ke Kalovu 2027/3, Prague, 12116, Czech Republic
| | | | - Tomas Jungwirth
- Institute of Physics, Czech Academy of Sciences, Cukrovarnicka 10, Praha, 6, 162 00, Czech Republic
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Martin Wolf
- Department of Physical Chemistry, Fritz-Haber-Institute of the Max-Planck-Society, Berlin, 14195, Germany
| | - Ilie Radu
- Department of Physics, Freie Universität Berlin, Berlin, 14195, Germany
- Max-Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Str. 2A, Berlin, 12489, Germany
| | - Markus Münzenberg
- Institute of Physics, University of Greifswald, Greifswald, 17489, Germany
| | - Peter M Oppeneer
- Institute of Physics, Martin-Luther Universität Halle-Wittenberg, Halle (Saale), 06120, Germany
| | - Georg Woltersdorf
- Institute of Physics, Martin-Luther Universität Halle-Wittenberg, Halle (Saale), 06120, Germany
| | - Tobias Kampfrath
- Department of Physics, Freie Universität Berlin, Berlin, 14195, Germany
- Department of Physical Chemistry, Fritz-Haber-Institute of the Max-Planck-Society, Berlin, 14195, Germany
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Luo C, Ryll H, Back CH, Radu F. X-ray magnetic linear dichroism as a probe for non-collinear magnetic state in ferrimagnetic single layer exchange bias systems. Sci Rep 2019; 9:18169. [PMID: 31796813 PMCID: PMC6890699 DOI: 10.1038/s41598-019-54356-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 11/11/2019] [Indexed: 11/09/2022] Open
Abstract
Ferrimagnetic alloys are extensively studied for their unique magnetic properties leading to possible applications in perpendicular magnetic recording, due to their deterministic ultrafast switching and heat assisted magnetic recording capabilities. On a prototype ferrimagnetic alloy we demonstrate fascinating properties that occur close to a critical temperature where the magnetization is vanishing, just as in an antiferromagnet. From the X-ray magnetic circular dichroism measurements, an anomalous 'wing shape' hysteresis loop is observed slightly above the compensation temperature. This bears the characteristics of an intrinsic exchange bias effect, referred to as atomic exchange bias. We further exploit the X-ray magnetic linear dichroism (XMLD) contrast for probing non-collinear states which allows us to discriminate between two main reversal mechanisms, namely perpendicular domain wall formation versus spin-flop transition. Ultimately, we analyze the elemental magnetic moments for the surface and the bulk parts, separately, which allows to identify in the phase diagram the temperature window where this effect takes place. Moreover, we suggests that this effect is a general phenomenon in ferrimagnetic thin films which may also contribute to the understanding of the mechanism behind the all optical switching effect.
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Affiliation(s)
- Chen Luo
- Helmholtz-Zentrum-Berlin für Materialen und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany. .,Institute of Experimental and Applied Physics, University of Regensburg, 93053, Regensburg, Germany. .,Institute of Experimental Physics of Functional Spin Systems, Technical University Munich, James-Franck-Str. 1, 85748, Garching b. München, Germany.
| | - Hanjo Ryll
- Helmholtz-Zentrum-Berlin für Materialen und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany
| | - Christian H Back
- Institute of Experimental and Applied Physics, University of Regensburg, 93053, Regensburg, Germany.,Institute of Experimental Physics of Functional Spin Systems, Technical University Munich, James-Franck-Str. 1, 85748, Garching b. München, Germany
| | - Florin Radu
- Helmholtz-Zentrum-Berlin für Materialen und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany.
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Hennecke M, Radu I, Abrudan R, Kachel T, Holldack K, Mitzner R, Tsukamoto A, Eisebitt S. Angular Momentum Flow During Ultrafast Demagnetization of a Ferrimagnet. PHYSICAL REVIEW LETTERS 2019; 122:157202. [PMID: 31050542 DOI: 10.1103/physrevlett.122.157202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Indexed: 06/09/2023]
Abstract
One of the key processes setting the speed of the ultrafast magnetization phenomena is the angular momentum transfer from and into the spin system. However, the way the angular momentum flows during ultrafast demagnetization and magnetization switching phenomena remains elusive so far. We report on time-resolved soft x-ray magnetic circular dichroism measurements of the ferrimagnetic GdFeCo alloy allowing us to record the dynamics of elemental spin and orbital moments at the Fe and Gd sites during femtosecond laser-induced demagnetization. We observe a complete transfer of spin and orbital angular momentum to the lattice during the first hundreds of femtoseconds of the demagnetization process.
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Affiliation(s)
- Martin Hennecke
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Ilie Radu
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Radu Abrudan
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Torsten Kachel
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Karsten Holldack
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Rolf Mitzner
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Arata Tsukamoto
- College of Science and Technology, Nihon University, 24-1 Narashinodai 7-chome, Funabashi-shi, Chiba 274-8501, Japan
| | - Stefan Eisebitt
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
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