Spin-charge coupled dynamics driven by a time-dependent magnetization

TL;DR

This paper investigates how dynamic magnetization in a thin metallic system influences coupled spin and charge transport, revealing new effects due to spin-orbit interaction and anisotropic spin relaxation.

Contribution

It derives comprehensive spin-charge kinetic equations accounting for inversion asymmetry and anisotropic relaxation, identifying a novel spin current-induced force term.

Findings

Identification of a new inverse spin filter force term.

Analysis of spin galvanic effect in a 2D limit.

Proposal of a measurement scheme to isolate specific contributions.

Abstract

The spin-charge coupled dynamics in a thin, magnetized metallic system are investigated. The effective driving force acting on the charge carriers is generated by a dynamical magnetic texture, which can be induced, e.g., by a magnetic material in contact with a normal-metal system. We consider a general inversion-asymmetric substrate/normal-metal/magnet structure, which, by specifying the precise nature of each layer, can mimick various experimentally employed setups. Inversion symmetry breaking gives rise to an effective Rashba spin-orbit interaction. We derive general spin-charge kinetic equations which show that such spin-orbit interaction, together with anisotropic Elliott-Yafet spin relaxation, yields significant corrections to the magnetization-induced dynamics. In particular, we present a consistent treatment of the spin density and spin current contributions to the equations of motion, inter alia identifying a novel term in the effective force which appears due to a spin current polarized parallel to the magnetization. This "inverse spin filter" contribution depends markedly on the parameter which describes the anisotropy in spin relaxation. To further highlight the physical meaning of the different contributions, the spin pumping configuration of typical experimental setups is analyzed in detail. In the two-dimensional limit the build-up of a DC voltage is dominated by the spin galvanic (inverse Edelstein) effect. A measuring scheme that could isolate this contribution is discussed.