On the origin of noncollinear magnetization coupling across RuX layers

TL;DR

This paper introduces an atomistic model for noncollinear magnetic coupling in multilayers with Ru alloy spacers, accurately predicting coupling behavior based on composition and thickness, surpassing previous models.

Contribution

The model accounts for three-dimensional atom-atom interactions in the spacer layer, improving quantitative predictions of magnetic coupling compared to earlier lateral-fluctuation models.

Findings

Accurately predicts bilinear and biquadratic coupling constants.

Shows noncollinear coupling even with infinitely stiff ferromagnetic layers.

Provides better quantitative agreement with experimental data.

Abstract

We present a simple atomistic model for the description of noncollinear coupling in magnetic multilayers with hybrid spacer layers made of Ru alloyed to ferromagnetic atoms such as Fe. In contrast to previous analytical and micromagnetic models that explain the noncollinear coupling by means of lateral fluctuations in the coupling constant, the presented model accounts for atom-atom coupling in all three spatial dimensions within the spacer layer. The new model is able to accurately predict the dependence of the macroscopic bilinear and biquadratic coupling constants on the spacer-layer composition and thickness, showing much better quantitative agreement than lateral-fluctuation models. Moreover, it predicts noncollinear coupling even for infinitely stiff ferromagnetic layers which goes beyond the predictions of previous models.