Calculating Spin Transport Properties From First Principles: Spin Currents

Local charge and spin currents are evaluated from the solutions of fully relativistic quantum mechanical scattering calculations for systems that include temperature-induced lattice and spin disorder as well as intrinsic alloy disorder. This makes it possible to determine material-specific spin transport parameters at finite temperatures. Illustrations are given for a number of important materials and parameters at 300 K. The spin-flip diffusion length l(sf) of Pt is determined from the exponential decay of a spin current injected into a long length of thermally disordered Pt; we find l(sf)(pt) = 5.3 +/- 0.4 nm. For the ferromagnetic substitutional disordered alloy permalloy (Py), we inject currents that are fully polarized parallel and antiparallel to the magnetization and calculate l(sf )from the exponential decay of their difference; we find l(sf)(py)= 2.8 +/- 0.1 nm. The transport polarization beta is found from the asymptotic polarization of a charge current in a long length of Py to be beta = 0.75 +/- 0.01. The spin Hall angle Theta(sH) is determined from the transverse spin current induced by the passage of a longitudinal charge current in thermally disordered Pt; our best estimate is Theta(Pt)(sH)= 4.5 +/- 1% corresponding to the experimental room-temperature bulk resistivity rho = 10.8 mu Omega cm.