Temperature dependent asymmetry of the nonlocal spin injection resistance: evidence for spin non-conserving interface scattering

We report nonlocal spin injection and detection experiments on mesoscopic Co-Al$_2$O$_3$-Cu spin valves. Spin precession in transverse fields (Hanle effect), as well as dependence of the nonlocal resistance on injector-detector magnetization alignment, have been studied. The spin diffusion length and the current spin polarization in Cu can be extracted from the measurements. We have also observed a temperature dependent asymmetry in the nonlocal resistance between parallel and antiparallel configurations of the magnetization of injector and detector. This suggests the existence of a nonequilibrium resistance that depends on the relative orientation of the detector magnetization and the nonequilibrium magnetization in the normal metal, providing evidence for increasing interface spin scattering with temperature.