Field- and damping-like spin-transfer torque in magnetic multilayers

TL;DR

This paper models spin-transfer torque in magnetic multilayers, analyzing how material parameters influence field-like and damping-like torques, which are crucial for spintronic device applications.

Contribution

It provides a detailed computational analysis of how exchange coupling affects spin-transfer torque components in multilayer structures.

Findings

Field-like torque varies significantly with exchange coupling strength.

Low coupling results in high field-like torque, high coupling can produce negative torque.

Dependence of torque on system parameters is key for device development.

Abstract

We investigate the spin-transfer torque in a magnetic multilayer structure by means of a spin-diffusion model. The torque in the considered system, consisting of two magnetic layers separated by a conducting layer, is caused by a perpendicular-to-plane current. We compute the strength of the field-like and the damping-like torque for different material parameters and geometries. Our studies suggest that the field-like torque highly depends on the exchange coupling strength of the itinerant electrons with the magnetization both in the pinned and the free layer. While a low coupling leads to very high field-like torques, a high coupling leads to low or even negative field-like torques. The dependence of the different torque terms on system parameters is considered very important for the development of applications such as STT MRAM and spin-torque oscillators.