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Yamazaki, Takumi*; Hirai, Takamasa*; Yagi, Takashi*; Yamashita, Yuichiro*; Uchida, Kenichi*; Seki, Takeshi*; Takanashi, Koki
Physical Review Applied (Internet), 21(2), p.024039_1 - 024039_11, 2024/02
Times Cited Count：0 Percentile：0.01(Physics, Applied)Hirohata, Atsufumi*; Lloyd, D. C.*; Kubota, Takahide*; Seki, Takeshi*; Takanashi, Koki; Sukegawa, Hiroaki*; Wen, Z.*; Mitani, Seiji*; Koizumi, Hiroki*
IEEE Access, 11, p.117443 - 117459, 2023/10
Masuda, Hiroto*; Yamane, Yuta*; Seki, Takeshi*; Raab, K.*; Dohi, Takaaki*; Modak, R.*; Uchida, Kenichi*; Ieda, Junichi; Kl
ui, M.*; Takanashi, Koki
Applied Physics Letters, 122(16), p.162402_1 - 162402_7, 2023/04
Times Cited Count：1 Percentile：49.29(Physics, Applied)Zhou, Z.*; Frost, W.*; Lloyd, D. C.*; Seki, Takeshi*; Kubota, Takahide*; Ramos, R.*; Saito, Eiji; Takanashi, Koki; Hirohata, Atsufumi*
Journal of Magnetism and Magnetic Materials, 571, p.170575_1 - 170575_5, 2023/04
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)Masuda, Hiroto*; Seki, Takeshi*; Yamane, Yuta*; Modak, R.*; Uchida, Kenichi*; Ieda, Junichi; Lau, Y.-C.*; Fukami, Shunsuke*; Takanashi, Koki
Physical Review Applied (Internet), 17(5), p.054036_1 - 054036_9, 2022/05
Times Cited Count：6 Percentile：70.93(Physics, Applied)The antisymmetric interlayer exchange coupling (AIEC) was recently discovered, playing pivotal roles in magnetization switching of a synthetic antiferromagnet (SAF) through inducing magnetization canting. Large AIEC is reported for perpendicularly magnetized Pt/Co/Ir/Co/Pt with wedge-shaped layers. The effective field of the AIEC is related with symmetric interlayer exchange coupling, providing guides to enhance the AIEC. We develop an extended Stoner-Wohlfarth model for a SAF, revealing key factors in its magnetization switching. Combining the theoretical knowledge and the experimental results, perpendicular magnetization switching is achieved solely by an in-plane magnetic field.
Frost, W.*; Seki, Takeshi*; Kubota, Takahide*; Ramos, R.*; Saito, Eiji; Takanashi, Koki*; Hirohata, Atsufumi*
Applied Physics Letters, 118(17), p.172405_1 - 172405_5, 2021/04
Times Cited Count：1 Percentile：7.45(Physics, Applied)Zhou, W.*; Seki, Takeshi*; Imamura, Hiroshi*; Ieda, Junichi; Takanashi, Koki*
Physical Review B, 100(9), p.094424_1 - 094424_5, 2019/09
Times Cited Count：6 Percentile：32.35(Materials Science, Multidisciplinary)Uchida, Kenichi*; Kikkawa, Takashi*; Seki, Takeshi*; Oyake, Takafumi*; Shiomi, Junichiro*; Qiu, Z.*; Takanashi, Koki*; Saito, Eiji
Physical Review B, 92(9), p.094414_1 - 094414_6, 2015/09
Times Cited Count：87 Percentile：93.34(Materials Science, Multidisciplinary)Seki, Takeshi*; Uchida, Kenichi*; Kikkawa, Takashi*; Qiu, Z.*; Saito, Eiji; Takanashi, Koki*
Applied Physics Letters, 107(9), p.092401_1 - 092401_4, 2015/08
Times Cited Count：39 Percentile：81.4(Physics, Applied)Zhang, H.; Yamamoto, Shunya; Fukaya, Yuki; Maekawa, Masaki; Li, H.; Kawasuso, Atsuo; Seki, Takeshi*; Saito, Eiji*; Takanashi, Koki*
Scientific Reports (Internet), 4, p.4844_1 - 4844_5, 2014/04
Times Cited Count：40 Percentile：81.69(Multidisciplinary Sciences)Kawasuso, Atsuo; Fukaya, Yuki; Maekawa, Masaki; Zhang, H.; Seki, Takeshi*; Yoshino, Tatsuro*; Saito, Eiji*; Takanashi, Koki*
Journal of Magnetism and Magnetic Materials, 342, p.139 - 143, 2013/09
Times Cited Count：19 Percentile：62.26(Materials Science, Multidisciplinary)Transversely spin-polarized positrons were injected near Pt and Au surfaces under an applied electric current. The three-photon annihilation of spin-triplet positronium, which was emitted from the surfaces into vacuum, was observed. When the positron spin polarization was perpendicular to the current direction, the maximum asymmetry of the three-photon annihilation intensity was observed upon current reversal for the Pt surfaces, whereas it was significantly reduced for the Au surface. The experimental results suggest that electrons near the Pt surfaces were in-plane and transversely spin-polarized with respect to the direction of the electric current. The maximum electron spin polarization was estimated to be more than 0.01 (1%).
Gu, B.; Sugai, Isamu*; Ziman, T.*; Guo, G. Y.*; Nagaosa, Naoto; Seki, Takeshi*; Takanashi, Koki; Maekawa, Sadamichi
Physical Review Letters, 105(21), p.216401_1 - 216401_4, 2010/11
Times Cited Count：71 Percentile：90.34(Physics, Multidisciplinary)Fukaya, Yuki; Maekawa, Masaki; Mochizuki, Izumi; Seki, Takeshi*; Takanashi, Koki*; Yoshino, Tatsuro*; Saito, Eiji; Kawasuso, Atsuo
no journal, ,
no abstracts in English
Fukaya, Yuki; Zhang, H.; Maekawa, Masaki; Mochizuki, Izumi; Seki, Takeshi*; Takanashi, Koki*; Yoshino, Tatsuro*; Saito, Eiji; Ieda, Junichi; Maekawa, Sadamichi; et al.
no journal, ,
no abstracts in English
Kawasuso, Atsuo; Fukaya, Yuki; Maekawa, Masaki; Zhang, H.; Hyodo, Toshio*; Wada, Ken*; Mochizuki, Izumi*; Seki, Takeshi*; Saito, Eiji*; Takanashi, Koki*
no journal, ,
no abstracts in English
Zhang, H.; Kawasuso, Atsuo; Fukaya, Yuki; Maekawa, Masaki; Seki, Takeshi*; Gu, B.; Ieda, Junichi; Maekawa, Sadamichi
no journal, ,
Zhang, H.; Fukaya, Yuki; Maekawa, Masaki; Li, H.; Kawasuso, Atsuo; Seki, Takeshi*; Yoshino, Tatsuro*; Saito, Eiji*; Takanashi, Koki*
no journal, ,
Kawasuso, Atsuo; Maekawa, Masaki; Fukaya, Yuki; Zhang, H.; Li, H.; Seki, Takeshi*; Saito, Eiji*; Takanashi, Koki*
no journal, ,
In this talk, we present (1) fundamental aspects of spin-polarized positron annihilation spectroscopy and (2) application of spin-polarized positron beam to current-induced spin polarization on heavy metal surfaces. Field-reversal asymmetry of Doppler broadening spectra for 3d ferromagnets is found to increase along with their magnetizations. Field-reversal asymmetry for 4f ferromagnets vanish above the Curie temperatures. The Doppler broadening spectra observed in magnetic fields exhibits the detailed features of ferromagnetic band structures. We also found that the positron annihilation lifetimes of 3d ferromagnets change upon field reversal. Using spin-polarized positron beams, we observed three-photon annihilation of positronium formed on heavy metal surfaces (Pt, Au, Cu) under application of DC current. We found a current-reversal asymmetry on three-photon annihilation intensity for Pt. This suggests that conduction electrons near the Pt surface are spin-polarized.
Kawasuso, Atsuo; Maekawa, Masaki; Fukaya, Yuki; Zhang, H.; Li, H.; Seki, Takeshi*; Saito, Eiji*; Takanashi, Koki*
no journal, ,
no abstracts in English
Zhang, H.; Yamamoto, Shunya; Li, H.; Fukaya, Yuki; Maekawa, Masaki; Kawasuso, Atsuo; Seki, Takeshi*; Saito, Eiji*; Takanashi, Koki*
no journal, ,
