Ultrafast demagnetization of Pt magnetic moment in L10-FePt probed by magnetic circular dichroism at a hard x-ray free electron laser

Kohei Yamamoto; Yuya Kubota; Motohiro Suzuki; Yasuyuki Hirata; Karel Carva; Marco Berritta; Kou Takubo; Yohei Uemura; Ryo Fukaya; Kenta Tanaka; Wataru Nishimura; Takuo Ohkochi; Tetsuo Katayama; Tadashi Togashi; Kenji Tamasaku; Makina Yabashi; Yoshihito Tanaka; Takeshi Seki; Koki Takanashi; Peter M Oppeneer; Hiroki Wadati

doi:10.1088/1367-2630/ab5ac2

New Journal of Physics (Jan 2019)

Ultrafast demagnetization of Pt magnetic moment in L10-FePt probed by magnetic circular dichroism at a hard x-ray free electron laser

Kohei Yamamoto,
Yuya Kubota,
Motohiro Suzuki,
Yasuyuki Hirata,
Karel Carva,
Marco Berritta,
Kou Takubo,
Yohei Uemura,
Ryo Fukaya,
Kenta Tanaka,
Wataru Nishimura,
Takuo Ohkochi,
Tetsuo Katayama,
Tadashi Togashi,
Kenji Tamasaku,
Makina Yabashi,
Yoshihito Tanaka,
Takeshi Seki,
Koki Takanashi,
Peter M Oppeneer,
Hiroki Wadati

Affiliations

Kohei Yamamoto: ORCiD; Institute for Solid State Physics, University of Tokyo , Kashiwanoha, Chiba 277-8581, Japan; Department of Physics, University of Tokyo , Hongo, Tokyo 113-0033, Japan; Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan
Yuya Kubota: Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan; RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
Motohiro Suzuki: Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
Yasuyuki Hirata: Institute for Solid State Physics, University of Tokyo , Kashiwanoha, Chiba 277-8581, Japan; Department of Physics, University of Tokyo , Hongo, Tokyo 113-0033, Japan
Karel Carva: ORCiD; Charles University , Faculty of Mathematics and Physics, Department of Condensed Matter Physics, Ke Karlovu 5, 121 16 Prague, Czech Republic
Marco Berritta: Department of Physics and Astronomy, Uppsala University , PO Box 516, SE-75120 Uppsala, Sweden
Kou Takubo: Institute for Solid State Physics, University of Tokyo , Kashiwanoha, Chiba 277-8581, Japan
Yohei Uemura: Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan
Ryo Fukaya: Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
Kenta Tanaka: Graduate School of Material Science, University of Hyogo , Kamigori, Hyogo 678-1297, Japan
Wataru Nishimura: Graduate School of Material Science, University of Hyogo , Kamigori, Hyogo 678-1297, Japan
Takuo Ohkochi: Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
Tetsuo Katayama: Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan; RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
Tadashi Togashi: Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan; RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
Kenji Tamasaku: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
Makina Yabashi: Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan; RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
Yoshihito Tanaka: Graduate School of Material Science, University of Hyogo , Kamigori, Hyogo 678-1297, Japan
Takeshi Seki: ORCiD; Institute for Materials Research, Tohoku University , Sendai, Miyagi 980-8577, Japan; Center for Spintronics Research Network, Tohoku University , Sendai, Miyagi 980-8577, Japan
Koki Takanashi: ORCiD; Institute for Materials Research, Tohoku University , Sendai, Miyagi 980-8577, Japan; Center for Spintronics Research Network, Tohoku University , Sendai, Miyagi 980-8577, Japan
Peter M Oppeneer: ORCiD; Department of Physics and Astronomy, Uppsala University , PO Box 516, SE-75120 Uppsala, Sweden
Hiroki Wadati: ORCiD; Institute for Solid State Physics, University of Tokyo , Kashiwanoha, Chiba 277-8581, Japan; Department of Physics, University of Tokyo , Hongo, Tokyo 113-0033, Japan; Graduate School of Material Science, University of Hyogo , Kamigori, Hyogo 678-1297, Japan

DOI: https://doi.org/10.1088/1367-2630/ab5ac2
Journal volume & issue: Vol. 21, no. 12
p. 123010

Abstract

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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. We demonstrate here the first ultrafast demagnetization dynamics in the ferromagnetic heavy 5d-transition metal Pt using circularly-polarized hard x-rays at an x-ray free electron laser (XFEL). The decay time of laser-induced demagnetization of L1 _0 -FePt is determined to be ${\tau }_{{\rm{Pt}}}=0.61\pm 0.04\,{\rm{ps}}$ using time-resolved x-ray magnetic circular dichroism at the Pt L _3 edge, whereas magneto-optical Kerr measurements indicate the decay time for the total magnetization as ${\tau }_{{\rm{total}}}\lt 0.1\,\mathrm{ps}$ . A transient magnetic state with 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 atomic spin dynamics contributions.

Published in New Journal of Physics

ISSN: 1367-2630 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Physics
Website: https://iopscience.iop.org/journal/1367-2630

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