Bias dependence of magnetic exchange interactions: application to interlayer exchange coupling in spin valves

TL;DR

This paper investigates how bias voltage influences magnetic exchange interactions, deriving a general expression and analyzing different systems like metallic and tunneling spin valves, revealing oscillatory and quadratic bias dependencies.

Contribution

It provides a new theoretical framework for understanding bias dependence of magnetic exchange interactions in spin valves, including conditions for quadratic behavior.

Findings

Interlayer exchange coupling in metallic systems shows weak oscillatory bias dependence.

In tunneling systems, the bias dependence is quadratic.

Derived an approximate expression for bias dependence in a toy model.

Abstract

We study how a bias voltage changes magnetic exchange interactions. We derive a general expression for magnetic exchange interactions for systems coupled to reservoirs under a bias potential, and apply it to spin valves. We find that for metallic systems, the interlayer exchange coupling shows a weak, oscillatory dependence on the bias potential. For tunneling systems, we find a quadratic dependence on the bias potential, and derive an approximate expression for this bias dependence for a toy model. We give general conditions for when the interlayer exchange coupling is a quadratic function of bias potential.