Total-reflection high-energy positron diffraction (TRHEPD) for structure determination of the topmost and immediate sub-surface atomic layers

Fukaya, Yuki; Kawasuso, Atsuo*; Ichimiya, Ayahiko*; Hyodo, Toshio*

Journal of Physics D; Applied Physics, 52(1), p.013002_1 - 013002_19, 2019/01

https://doi.org/10.1088/1361-6463/aadf14

no abstracts in English

Structure determination of the rutile-TiO(110)(12) surface using total-reflection high-energy positron diffraction (TRHEPD)

Mochizuki, Izumi*; Ariga, Hiroko*; Fukaya, Yuki; Wada, Ken*; Maekawa, Masaki*; Kawasuso, Atsuo*; Shidara, Tetsuo*; Asakura, Kiyotaka*; Hyodo, Toshio*

Hyomen Kagaku, 37(9), p.451 - 456, 2016/09

https://doi.org/10.1380/jsssj.37.451

no abstracts in English

Applications of spin-polarized positron beam

Kawasuso, Atsuo

Hoshasen To Sangyo, (139), p.18 - 22, 2015/12

no abstracts in English

Charge-to-spin conversion and spin diffusion in Bi/Ag bilayers observed by spin-polarized positron beam

Zhang, H. J.; Yamamoto, Shunya; Gu, B.; Li, H.; Maekawa, Masaki; Fukaya, Yuki; Kawasuso, Atsuo

Physical Review Letters, 114(16), p.166602_1 - 166602_5, 2015/04

https://doi.org/10.1103/PhysRevLett.114.166602

Charge-to-spin conversion induced by the Rashba-Edelstein effect was directly observed for the first time in samples with no magnetic layer. A spin-polarized positron beam was used to probe the spin polarization of the outermost surface electrons of Bi/Ag/AlO and Ag/Bi/AlO when charge currents were only associated with the Ag layers. An opposite surface spin polarization was found between Bi/Ag/AlO and Ag/Bi/AlO samples with the application of a charge current in the same direction. The surface spin polarizations of both systems decreased exponentially with the outermost layer thickness, suggesting the occurrence of spin diffusion from the Bi/Ag interface to the outermost surfaces. This work provides a new technique to measure spin diffusion length.

Radioisotope-based spin-polarized positron beam

Kawasuso, Atsuo

Yodenshi Kagaku, (4), p.9 - 22, 2015/02

http://positron-science.org/kaiho/public/04gou/04_09.pdf

In this article, I report, the spin polarization of positrons emitted from radioisotopes, the development of spin-polarized beams, the fundamental aspects of spin-polarized positron annihilation method, and, the investigation of current-induced spin polarization on metal surfaces through the spin-polarized positronium annihilation.

Total reflection high-energy positron diffraction; An Ideal diffraction technique for surface structure analysis

Fukaya, Yuki; Maekawa, Masaki; Kawasuso, Atsuo; Mochizuki, Izumi*; Wada, Ken*; Shidara, Tetsuo*; Ichimiya, Ayahiko*; Hyodo, Toshio*

Applied Physics Express, 7(5), p.056601_1 - 056601_4, 2014/05

https://doi.org/10.7567/APEX.7.056601

no abstracts in English

Spin polarizations of positron beams generated using electrostatic and magnetic transportation systems with Ge and Na sources

Maekawa, Masaki; Fukaya, Yuki; Zhang, H.; Li, H.; Kawasuso, Atsuo

Journal of Physics; Conference Series, 505, p.012033_1 - 012033_4, 2014/04

https://doi.org/10.1088/1742-6596/505/1/012033

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

https://doi.org/10.1038/srep04844

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%).

Spin-polarized positron annihilation spectroscopy for spintronics applications

Kawasuso, Atsuo; Fukaya, Yuki; Maekawa, Masaki; Mochizuki, Izumi; Zhang, H.

Journal of Physics; Conference Series, 443(1), p.012084_1 - 012084_4, 2013/06

https://doi.org/10.1088/1742-6596/443/1/012084

Spin-polarized positrons are useful in studying spintronics materials. We are producing positron sources for highly polarized positrons and are developing polarized positron beams using those sources. We investigated some ferromagnets and found that their electron momentum distributions exhibit field-reversal asymmetry. We also found a strong current-induced spin accumulation on Pt surfaces.