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

Spin-polarized positron beam, 2; Applications to spintronics

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.