Speaker
Atsuo Kawasuso
(QST)
Description
Positrons emitted from radioisotopes are longitudinally spin-polarized due to parity non-conservation in the weak interaction. In 1960's, the angular correlation of annihilation radiation measurement with spin-polarized positrons was demonstrated to be useful in studying the ferromagnetic band structures. In 1982, the first experiment on surface ferromagnetism with spin-polarized positron beam was reported by the Michigan group. This work demonstrated the existence of ferromagnetism on the Ni first surface layer against the magnetic dead layer hypothesis. There might be many potential applications of spin-polarized positron beam in rapidly progressing spintronics field. However, after the Michigan group only a limited number of works have been carried out. We have been developing radioisotope (22Na, 68Ge)-based polarized positron beams. In this talk, we introduce the current status of our beam development and its applications to (i) ferromagnets (both bulk and surface) [1-3], (ii) strong spin-orbit interaction systems [4-6] and (iii) high-spin state vacancy systems [7].
[1] A. Kawasuso et al., Phys. Rev. B83 (2011)100406(R), Phys. Rev. B85 (2012)024417(6).
[2] H. Li et al., J. Phys. Condens. Matter 27(2015)246001-1-5.
[3] H. Li et al, Defect and Diffusion Forum, 373(2017)65-70.
[4] A. Kawasuso et al., J. Mag. Mag. Mater. 342(2013)139-143.
[5] H. J. Zhang et al., Scientific Reports 4(2014)04844.
[6] H. J. Zhang et al., Phys. Rev. Lett. 114(2015)166602-1-5.
[7] M. Maekawa et al., Appl. Phys. Lett., 110(2017)172402-1-5.
Primary author
Atsuo Kawasuso
(QST)
