Spin transport at finite temperatures: A first-principles study for ferromagnetic vertical bar nonmagnetic interfaces

Symmetry lowering at an interface leads to an enhancement of the effect of spin-orbit coupling and to a discontinuity of spin currents passing through the interface. This discontinuity is characterized by a "spin-memory loss" (SML) parameter delta that has only been determined directly at low temperatures. Although delta is believed to be significant in experiments involving interfaces between ferromagnetic and nonmagnetic metals, especially heavy metals like Pt, it is more often than not neglected to avoid introducing too many unknown interface parameters in addition to often poorly known bulk parameters like the spin-flip diffusion length l(sf). In this work, we calculate delta along with the interface resistance ARI and the spin-asymmetry parameter gamma as a function of temperature for Co vertical bar Pt and Py vertical bar Pt interfaces where Py is the ferromagnetic Ni80Fe20 alloy, permalloy. We use first-principles scattering theory to calculate the conductance as well as local charge and spin currents, modeling temperature-induced disorder with frozen thermal lattice and, for ferromagnetic materials, spin disorder within the adiabatic approximation. The bulk and interface parameters are extracted from the spin currents using a Valet-Fert model generalized to include SML.