@article{702a19773c664ab6a2a0cdd1cb963450,
title = "Ultrafast demagnetization of Pt magnetic moment in L10-FePt probed by magnetic circular dichroism at a hard x-ray free electron laser",
abstract = "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 L10-FePt is determined to be τpt = 0.61 ± 0.04 using time-resolved x-ray magnetic circular dichroism at the Pt L3 edge, whereas magneto-optical Kerr measurements indicate the decay time for the total magnetization as τtotal < 0.1. 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.",
keywords = "XFEL, photo-induced magnetization dynamics, time-resolved XMCD",
author = "Kohei Yamamoto and Yuya Kubota and Motohiro Suzuki and Yasuyuki Hirata and Karel Carva and Marco Berritta and Kou Takubo and Yohei Uemura and Ryo Fukaya and Kenta Tanaka and Wataru Nishimura and Takuo Ohkochi and Tetsuo Katayama and Tadashi Togashi and Kenji Tamasaku and Makina Yabashi and Yoshihito Tanaka and Takeshi Seki and Koki Takanashi and Oppeneer, {Peter M.} and Hiroki Wadati",
note = "Funding Information: This work was partially supported by Toray Science and Technology Grant of Toray Research Foundation, MEXTQuantum Leap Flagship Program (MEXTQ-LEAP) Grant No. JPMXS0118068681 and JSPS KAKENHI Grant No.19H05824, 19H01816, 17K14334, 17H02823.Wefurther acknowledge financial support from the Swedish Research Council (VR), theKand A Wallenberg Foundation (Grant No. 2 015.006 0), and the Czech Science Foundation (Grant No. 18-07172S), and computer time received from the Swedish National Infrastructure for Computing (SNIC). The XFEL experiments were performed at SACLA with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal No. 2017B8060, 2017B8088). The synchrotron radiation experiments were performed at BL19LSU in SPring-8 with the approval of RIKEN (Proposal No. 20160106, 20170033). The authors would like to acknowledge the supporting members of the SACLA facility. KY acknowledges support from the ALPS program of the University of Tokyo. Publisher Copyright: {\textcopyright} 2019 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft.",
year = "2019",
month = dec,
day = "12",
doi = "10.1088/1367-2630/ab5ac2",
language = "English",
volume = "21",
journal = "New Journal of Physics",
issn = "1367-2630",
publisher = "IOP Publishing Ltd.",
number = "12",
}