Different spin relaxation mechanisms between epitaxial and polycrystalline Ta thin films

We demonstrate that spin relaxation mechanisms are different between epitaxial Ta and disordered polycrystalline Ta thin films by determining the relationship between spin relaxation time and diffusion constant. To control the diffusion constant, epitaxial Ta and polycrystalline Ta thin films are prepared by sputtering on different substrates and at different growth temperatures. The spin relaxation time is extracted from the results of weak antilocalization analysis including the superconducting fluctuation effect. The dominant spin relaxation mechanism for polycrystalline Ta thin films is the Elliot-Yafet mechanism, as is expected for centrosymmetric metal films. In contrast, the D'yakonov-Perel' mechanism plays a role in epitaxial Ta thin films. (C) 2017 The Japan Society of Applied Physics