Predicting the Spin-Lattice Order of Frustrated Systems from First-Principles

TL;DR

This paper introduces a first-principles method to analyze spin-lattice interactions in magnetic solids, accurately predicting ground state structures and magnetic configurations in frustrated systems.

Contribution

It presents a new computational approach to evaluate spin interactions and their derivatives from density functional theory, improving understanding of spin-lattice coupling in frustrated magnets.

Findings

Predicted tetragonal distortion of MgCr2O4 consistent with experiments.

Found collinear spin ground state as lowest energy, contrasting previous models.

Efficiently evaluated spin exchange and Dzyaloshinskii-Moriya interactions from first principles.

Abstract

A novel general method of describing the spin-lattice interactions in magnetic solids was proposed in terms of first principles calculations. The spin exchange and Dzyaloshinskii-Moriya interactions as well as their derivatives with respect to atomic displacements can be evaluated efficiently on the basis of density functional calculations for four ordered spin states. By taking into consideration the spin-spin interactions, the phonons, and the coupling between them, we show that the ground state structure of a representative spin-frustrated spinel, MgCr2 O4, is tetragonally distorted, in agreement with experiments. However, our calculations find the lowest energy for the collinear spin ground state, in contrast to previously suggested non-collinear models.