Scattering Theory of Charge-Current Induced Magnetization Dynamics

TL;DR

This paper introduces a new scattering theory to analyze how charge currents induce magnetization dynamics in ferromagnetic heterostructures, successfully predicting low-current switching consistent with experiments.

Contribution

The authors develop a general scattering formalism for charge current induced magnetization torques in layered ferromagnetic systems, applicable to complex materials.

Findings

Predicted magnetization switching at low current densities (~5×10^6 A/cm^2)

Theoretical results agree with recent experimental observations

Demonstrated the formalism's applicability to GaAs/(Ga,Mn)As systems

Abstract

In ferromagnets, charge currents can excite magnons via the spin-orbit coupling. We develop a novel and general scattering theory of charge current induced macrospin magnetization torques in normal metal$|$ferromagnet$|$normal metal layers. We apply the formalism to a dirty GaAs$|$(Ga,Mn)As$|$GaAs system. By computing the charge current induced magnetization torques and solving the Landau-Lifshitz-Gilbert equation, we find magnetization switching for current densities as low as $ 5\times 10^{6}$~A/cm$^2$. Our results are in agreement with a recent experimental observation of charge-current induced magnetization switching in (Ga,Mn)As.