Exchange Interactions in Paramagnetic Amorphous and Disordered Crystalline CrN-based Systems

TL;DR

This paper introduces a first principles supercell method to calculate exchange interactions in disordered magnetic systems, revealing strong local environment effects in crystalline, amorphous, and solid solution CrN-based materials.

Contribution

The paper develops a novel approach to compute exchange interactions in disordered magnetic materials considering local environment variations.

Findings

Strong local environment effects in all studied systems

Distance-dependent exchange interactions derived for crystalline and amorphous CrN

Identification of non-collinear magnetic ground state in amorphous CrN

Abstract

We present a first principles supercell methodology for the calculation of exchange interactions of magnetic materials with arbitrary degrees of structural and chemical disorder in their high temperature paramagnetic state. It is based on a projection of the total magnetic energy of the system onto local pair clusters, allowing the interactions to vary independently as a response to their local environments. We demonstrate our method by deriving the distance dependent exchange interactions in vibrating crystalline CrN, a Ti$_{0.5}$Cr$_{0.5}$N solid solution as well as in amorphous CrN. Our method reveals strong local environment effects in all three systems. In the amorphous case we use the full set of exchange interactions in a search for the non-collinear magnetic ground state.