Spin torque and waviness in magnetic multilayers: a bridge between Valet-Fert theory and quantum approaches

TL;DR

This paper introduces a unified theoretical framework for spin transport in magnetic multilayers, bridging classical Valet-Fert theory and quantum scattering approaches, and applies it to non-collinear spin valves.

Contribution

It develops a simple, adaptable theory connecting Landauer-Buttiker formalism with classical and generalized circuit theories for magnetic multilayers.

Findings

The theory maps onto Valet-Fert for collinear systems.

It extends to non-collinear systems without spin-flip scattering.

Applied to spin valves, it explains angular dependence of spin accumulation and torque.

Abstract

We develop a simple theoretical framework for transport in magnetic multilayers, based on Landauer-Buttiker scattering formalism and Random Matrix Theory. A simple transformation allows one to go from the scattering point of view to theories expressed in terms of local currents and electrochemical potential. In particular, our theory can be mapped onto the well established classical Valet Fert theory for collinear systems. For non collinear systems, in the absence of spin-flip scattering, our theory can be mapped onto the generalized circuit theory. We apply our theory to the angular dependance of spin accumulation and spin torque in non-collinear spin valves.