First principles study on the spin transfer torques

TL;DR

This paper presents a first principles computational method for calculating spin transfer torques in layered magnetic systems, revealing material-dependent behaviors and the impact of interfacial disorder.

Contribution

A new first principles approach for calculating spin transfer torques in noncollinear layered systems is introduced, incorporating scattering wave functions and material-specific properties.

Findings

Ni exhibits longer spin injection length than Co.

Interfacial disorder can enhance spin transfer torques.

Material dependence explained by Fermi surface analysis.

Abstract

An efficient first principles method was developed to calculate spin transfer torques in layered system with noncollinear magnetization. The complete scattering wave function is determined by matching the wave function in the scattering region with the Bloch states in the leads. The spin transfer torques are obtained with aid of the scattering wave function. We applied our method to the ferromagnetic spin valve and found that the material (Co, Ni and Ni80Fe20) dependence of the spin transfer torques could be well understood by the Fermi surface. Ni has much longer spin injection penetration length than Co. Interfacial disorder is also considered. It is found that the spin transfer torques could be enhanced by the interfacial disorder in some system.