Surface spin polarization of ferromagnets observed by a spin-polarized positron beam

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

Surface magnetic properties attract extraordinary interest due to their important role in future device tech-nologies. Spin-polarized positron beam (SP-PB), with both high sensitivity and depth selectivity to polarized electrons in materials, is a suitable probe to detect polarized electrons leading to magnetism and spin-related phenomena at surfaces, interfaces and thin films. We investigated surface spin polarization of conventional ferro-magnets (Fe, Co, and Ni) by a newly developed SP-PB with about 47% spin polarization. The obtained results for Fe (1000 nm) /MgO and Ni (1000 nm) /MgO are 6.5% and -6.1%, respectively. The spin polarizaition of Feis positive, however, Ni shows negative spin polarization. The underlying mechanism will be discussed.