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

https://doi.org/10.1103/PhysRevApplied.17.054036

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.

Microstructures and interface magnetic moments in MnVAl/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

https://doi.org/10.3390/nano11071723

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

AA2019-0172.pdf:1.08MB

https://doi.org/10.1103/PhysRevB.100.094424

Preferred site occupation of 3 atoms in NiFeN ( = 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

https://doi.org/10.1103/PhysRevMaterials.2.024407

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

https://doi.org/10.1063/1.4929691

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

https://doi.org/10.1016/j.jmmm.2013.04.006

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%).

Effect of cotunneling and spin polarization on the large tunneling magnetoresistance effect in granular C-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

https://doi.org/10.1103/PhysRevB.83.174422

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

https://doi.org/10.1103/PhysRevLett.105.216401

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/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/Co hybrid material is necessary. Absorption spectra of CCo are different from that of pristine C. In particular, peak intensity corresponding to (LUMO) C 1s excitation of CCo is clearly attenuated. In addition, C 1s photoelectron peak of CCo slightly shifted to lower binding energy compared to that of pristine C. These results indicate that 3d electron of Co transfers to orbital of C and new electronic states are formed in the C-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 and Co.

Magnetic and magnetotransport properties in nanogranular Co/C-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

https://doi.org/10.2320/matertrans.48.754

Magnetic properties were investigated for the alternately deposited film of C 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.