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Journal Articles

Magnetization switching process by dual spin-orbit torque in interlayer exchange-coupled systems

Masuda, Hiroto*; Yamane, Yuta*; Seki, Takeshi*; Raab, K.*; Dohi, Takaaki*; Modak, R.*; Uchida, Kenichi*; Ieda, Junichi; Kl$"a$ui, M.*; Takanashi, Koki

Applied Physics Letters, 122(16), p.162402_1 - 162402_7, 2023/04

Journal Articles

Large antisymmetric interlayer exchange coupling enabling perpendicular magnetization switching by an in-plane magnetic field

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:1 Percentile:48.88(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.

Journal Articles

Magnetoelastic anisotropy in Heusler-type Mn$$_{2-delta}$$CoGa$$_{1+delta}$$ films

Kubota, Takahide*; Takano, Daichi*; Kota, Yohei*; Mohanty, S.*; Ito, Keita*; Matsuki, Mitsuhiro*; Hayashida, Masahiro*; Sun, M.*; Takeda, Yukiharu; Saito, Yuji; et al.

Physical Review Materials (Internet), 6(4), p.044405_1 - 044405_12, 2022/04

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

Microstructures and interface magnetic moments in Mn$$_{2}$$VAl/Fe layered films showing exchange bias

Kubota, Takahide*; Shimada, Yusuke*; Tsuchiya, Tomoki*; Yoshikawa, Tomoki*; Ito, Keita*; Takeda, Yukiharu; Saito, Yuji; Konno, Toyohiko*; Kimura, Akio*; Takanashi, Koki*

Nanomaterials (Internet), 11(7), p.1723_1 - 1723_11, 2021/07

 Times Cited Count:2 Percentile:30.62(Chemistry, Multidisciplinary)

Journal Articles

Evaluation of edge domains in giant magnetoresistive junctions

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:0(Physics, Applied)

Journal Articles

Spinmotive force in the out-of-plane direction generated by spin wave excitations in an exchange-coupled bilayer element

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:4 Percentile:26.71(Materials Science, Multidisciplinary)

Journal Articles

Mn$$_{2}$$VAl Heusler alloy thin films; Appearance of antiferromagnetism and exchange bias in a layered structure with Fe

Tsuchiya, Tomoki*; Kobayashi, Ryota*; Kubota, Takahide*; Saito, Kotaro*; Ono, Kanta*; Ohara, Takashi; Nakao, Akiko*; Takanashi, Koki*

Journal of Physics D; Applied Physics, 51(6), p.065001_1 - 065001_7, 2018/02

 Times Cited Count:7 Percentile:34.18(Physics, Applied)

Journal Articles

Preferred site occupation of 3$$d$$ atoms in Ni$$_{x}$$Fe$$_{4-x}$$N (${it x}$ = 1 and 3) films revealed by X-ray absorption spectroscopy and magnetic circular dichroism

Takata, Fumiya*; Ito, Keita*; Takeda, Yukiharu; Saito, Yuji; Takanashi, Koki*; Kimura, Akio*; Suemasu, Takashi*

Physical Review Materials (Internet), 2(2), p.024407_1 - 024407_5, 2018/02

 Times Cited Count:14 Percentile:53.87(Materials Science, Multidisciplinary)

Journal Articles

Enhancement of anomalous Nernst effects in metallic multilayers free from proximity-induced magnetism

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:75 Percentile:92.94(Materials Science, Multidisciplinary)

Journal Articles

Observation of inverse spin Hall effect in ferromagnetic FePt alloys using spin Seebeck effect

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:35 Percentile:81.06(Physics, Applied)

Journal Articles

Current-induced spin polarization on metal surfaces probed by spin-polarized positron beam

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:36 Percentile:81.6(Multidisciplinary Sciences)

Journal Articles

Current-induced spin polarization on a Pt surface; A New approach using spin-polarized positron annihilation spectroscopy

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:64.04(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%).

Journal Articles

Bias voltage dependence of tunneling magnetoresistance in granular C$$_{60}$$-Co films with current-perpendicular-to-plane geometry

Sakai, Seiji; Mitani, Seiji*; Matsumoto, Yoshihiro; Entani, Shiro; Avramov, P.; Otomo, Manabu; Naramoto, Hiroshi*; Takanashi, Koki

Journal of Magnetism and Magnetic Materials, 324(12), p.1970 - 1974, 2012/06

 Times Cited Count:3 Percentile:15.42(Materials Science, Multidisciplinary)

Journal Articles

Effect of cotunneling and spin polarization on the large tunneling magnetoresistance effect in granular C$$_{60}$$-Co films

Sakai, Seiji; Mitani, Seiji*; Sugai, Isamu; Takanashi, Koki; Matsumoto, Yoshihiro; Entani, Shiro; Naramoto, Hiroshi*; Avramov, P.; Maeda, Yoshihito

Physical Review B, 83(17), p.174422_1 - 174422_6, 2011/05

 Times Cited Count:8 Percentile:37.22(Materials Science, Multidisciplinary)

Journal Articles

Spin pumping efficiency from half metallic Co$$_2$$MnSi

Chudo, Hiroyuki; Ando, Kazuya*; Saito, Kesami*; Okayasu, Satoru; Haruki, Rie; Sakuraba, Yuya*; Yasuoka, Hiroshi; Takanashi, Koki; Saito, Eiji

Journal of Applied Physics, 109(7), p.073915_1 - 073915_4, 2011/04

 Times Cited Count:19 Percentile:62.57(Physics, Applied)

We present spin pumping using a Heusler alloy Co$$_2$$MnSi/Pt bilayer film. A spin current is produced by a ferromagnetic resonance (FMR) technique. The pure spin current injected into the Pt layer from the Co$$_2$$MnSi layer is detected by the inverse spin-Hall effect (ISHE), which converts the spin current into an electric current. We estimated a damping constant of the Co$$_2$$MnSi/Pt bilayer film from an angular dependence of FMR spectra. Using the damping constant efficiency of spin pumping from the Co$$_2$$MnSi layer is evaluated. We found that a mixing conductance at the Co$$_2$$MnSi/Pt interface is comparable to that at a permalloy/Pt interface.

Journal Articles

Surface-assisted spin Hall effect in Au films with Pt impurities

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:69 Percentile:90.53(Physics, Multidisciplinary)

Journal Articles

Composition dependence of magnetic and magnetotransport properties in C$$_{60}$$-Co granular thin films

Sugai, Isamu*; Sakai, Seiji; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Mitani, Seiji*; Takanashi, Koki; Maeda, Yoshihito

Journal of Applied Physics, 108(6), p.063920_1 - 063920_7, 2010/09

 Times Cited Count:8 Percentile:35.22(Physics, Applied)

Journal Articles

The Electronic structures of fullerene/transition-metal hybrid material

Matsumoto, Yoshihiro; Sakai, Seiji; Naramoto, Hiroshi*; Hirao, Norie*; Baba, Yuji; Shimada, Toshihiro*; Sugai, Isamu; Takanashi, Koki; Maeda, Yoshihito

Materials Research Society Symposium Proceedings, Vol.1081 (Internet), 6 Pages, 2008/03

Recently, we have found the appearance of substantial MR ratio (80%) in a C$$_{60}$$/Co hybrid material. Such the MR ratio cannot be explained enough only by tunnel conduction through Co grains. Therefore, to obtain information about electronic structures of C$$_{60}$$/Co hybrid material is necessary. Absorption spectra of C$$_{60}$$Co are different from that of pristine C$$_{60}$$. In particular, peak intensity corresponding to $$pi$$ $$^*$$(LUMO) $$leftarrow$$ C 1s excitation of C$$_{60}$$Co is clearly attenuated. In addition, C 1s photoelectron peak of C$$_{60}$$Co slightly shifted to lower binding energy compared to that of pristine C$$_{60}$$. These results indicate that 3d electron of Co transfers to $$pi$$ $$^*$$ orbital of C$$_{60}$$ and new electronic states are formed in the C$$_{60}$$-Co compound. In fact, XPS spectra of valence excitation region also demonstrate the formation of hybrid orbital near the Fermi level due to the coupling of C$$_{60}$$ and Co.

Journal Articles

Giant tunnel magnetoresistance in codeposited fullerene-cobalt films in the low bias-voltage regime

Sakai, Seiji; Sugai, Isamu; Mitani, Seiji*; Takanashi, Koki; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Avramov, P.; Okayasu, Satoru; Maeda, Yoshihito

Applied Physics Letters, 91(24), p.242104_1 - 242104_3, 2007/12

 Times Cited Count:30 Percentile:72.58(Physics, Applied)

Journal Articles

Magnetic and magnetotransport properties in nanogranular Co/C$$_{60}$$-Co film with high magnetoresistance

Sakai, Seiji; Yakushiji, Kei*; Mitani, Seiji*; Sugai, Isamu; Takanashi, Koki*; Naramoto, Hiroshi*; Avramov, P.; Lavrentiev, V.*; Narumi, Kazumasa; Maeda, Yoshihito

Materials Transactions, 48(4), p.754 - 758, 2007/04

 Times Cited Count:8 Percentile:49.04(Materials Science, Multidisciplinary)

Magnetic properties were investigated for the alternately deposited film of C$$_{60}$$ and Co which has found to exhibit tunnel magnetoresistance (MR) of 10-80 %. Magnetic field and temperature dependences of magnetization showed typical superparamagnetic behaviors with the blocking temperature of 40 K. The magnetization curve at 300 K was well fitted by the Langevin function with the size distribution of Co particles, and the mean diameter and size distribution were evaluated to be 3.1 nm and 1 nm, respectively. Based on the magnetic properties, the detailed structure and magnetotransport properties are discussed.

86 (Records 1-20 displayed on this page)