MAELAS 2.0: A new version of a computer program for the calculation of magneto-elastic properties

TL;DR

MAELAS 2.0 introduces a more reliable method for calculating magnetoelastic constants, improving accuracy especially for non-cubic crystals, and includes updates for better robustness and additional clarifications.

Contribution

The paper presents an updated version of MAELAS with a new methodology for computing anisotropic magnetoelastic constants via linear energy-strain fitting, enhancing accuracy and robustness.

Findings

New linear fitting method is more reliable for non-cubic crystals.

Accuracy of previous method can be improved using deformation gradients from equilibrium strain.

Clarified the role of demagnetized state and derived saturation magnetostriction expressions.

Abstract

MAELAS is a computer program for the calculation of magnetocrystalline anisotropy energy, anisotropic magnetostrictive coefficients and magnetoelastic constants in an automated way. The method originally implemented in version 1.0 of MAELAS was based on the length optimization of the unit cell, proposed by Wu and Freeman, to calculate the anisotropic magnetostrictive coefficients. We present here a revised and updated version (v2.0) of MAELAS, where we added a new methodology to compute anisotropic magnetoelastic constants from a linear fitting of the energy versus applied strain. We analyze and compare the accuracy of both methods showing that the new approach is more reliable and robust than the one implemented in version 1.0, especially for non-cubic crystal symmetries. This analysis also help us to find that the accuracy of the method implemented in version 1.0 could be improved by using deformation gradients derived from the equilibrium magnetoelastic strain tensor, as well as potential future alternative methods like the strain optimization method. Additionally, we clarify the role of the demagnetized state in the fractional change in length, and derive the expression for saturation magnetostriction for polycrystals with trigonal, tetragonal and orthorhombic crystal symmetry. In this new version, we also fix some issues related to trigonal crystal symmetry found in version 1.0.