Automated calculations of exchange magnetostriction

TL;DR

This paper introduces a computational method and a Python package for calculating exchange magnetostriction properties from first-principles and models, correcting previous theoretical errors and enabling automated analysis.

Contribution

The paper presents a new methodology and implementation in MAELAS v3.0 for calculating exchange magnetostriction constants, correcting prior theoretical expressions, and facilitating automated first-principles and model computations.

Findings

Corrected the theoretical expression for $ ext{lambda}^{ ext{alpha 1,0}}$ in uniaxial crystals.

Implemented an automated computational tool in MAELAS v3.0.

Demonstrated the method's ability to compute magnetoelastic constants from first-principles.

Abstract

We present a methodology based on deformations of the unit cell that allows to compute the isotropic magnetoelastic constants, isotropic magnetostrictive coefficients and spontaneous volume magnetostriction associated to the exchange magnetostriction. This method is implemented in the python package MAELAS (v3.0), so that it can be used to obtain these quantities by first-principles calculations and classical spin-lattice models in an automated way. We show that the required reference state to obtain the spontaneous volume magnetostriction combines the equilibrium volume of the paramagnetic state and magnetic order of the ground state. We identify an error in the theoretical expression of the isotropic magnetostrictive coefficient $\lambda^{\alpha 1,0}$ for uniaxial crystals given in previous publications, which is corrected in this work. The presented computational tool may be helpful to provide a better understanding and characterization of the relationship between the exchange interaction and magnetoelasticity.