Antiferromagnetic CuMnAs: Ab initio description of finite temperature magnetism and resistivity

TL;DR

This paper develops ab initio models to describe finite-temperature magnetism and resistivity in antiferromagnetic CuMnAs, revealing how magnons and phonons influence electrical transport and magnetic moment canting.

Contribution

It introduces three computational models for spin fluctuations in AFM CuMnAs, including a relativistic disordered local moment approach and its generalization, applicable to impurity systems.

Findings

Resistivity decreases or saturates above 400 K due to magnons and phonons.

Electronic structure changes explain resistivity behavior at finite temperatures.

Impurities significantly affect residual resistivity and magnetic canting.

Abstract

Noncollinear magnetic moments in antiferromagnets (AFM) lead to a complex behavior of electrical transport, even to a decreasing resistivity due to an increasing temperature. Proper treatment of such phenomena is required for understanding AFM systems at finite temperatures; however first-principles description of these effects is complicated. With ab initio techniques, we investigate three models of spin fluctuations (magnons) influencing the transport in AFM CuMnAs; the models are numerically feasible and easily implementable to other studies. We numerically justified a fully relativistic collinear disordered local moment approach and we present its uncompensated generalization. A saturation or a decrease of resistivity caused by magnons, phonons, and their combination (above approx. 400 K) was observed and explained by changes in electronic structure. Within the coherent potential approximation, our finite-temperature approaches may be applied also to systems with impurities, which are found to have a large impact not only on residual resistivity, but also on canting of magnetic moments from the AFM to the ferromagnetic (FM) state.