Spin-lattice interaction parameters from first principles: theory and implementation

TL;DR

This paper introduces a first-principles scheme to calculate spin-lattice coupling parameters, enabling combined molecular-spin dynamics simulations and detailed analysis of magnetic anisotropy effects due to lattice distortions.

Contribution

The work provides a coherent method to derive atomic SLC parameters up to any order and analyzes their impact on exchange interactions and magnetic anisotropy from first principles.

Findings

Good agreement between SLC-derived and cluster-calculated SSC parameters.

Linear and quadratic SLC contributions significantly affect exchange properties.

Site-diagonal SLC parameters relate lattice distortions to magnetic anisotropy.

Abstract

A scheme is presented to calculate on a first-principles level the spin-lattice coupling (SLC) parameters needed to perform combined molecular-spin dynamics (MSD) simulations. By treating changes to the spin configuration and atomic positions on the same level, closed expressions for the atomic SLC parameters could be derived in a coherent way up to any order. The properties of the SLC parameters are discussed considering separately the symmetric and antisymmetric parts of the SLC tensor. The changes due to atomic displacements of the spin-spin exchange coupling (SSC) parameters estimated using the SLC parameters are compared with the SSC parameters calculated for an embedded cluster with the central atom displaced, demonstrating good agreement of these results. Moreover, this allows to study the impact of different SLC contributions, linear and quadratic with respect to displacements, on the properties of the modified SSC parameters. In addition, we represent an approach to calculate the site-diagonal SLC parameters characterizing local magnetic anisotropy induced by a lattice distortion, which is a counterpart of the approach based on magnetic torque used for the investigations of magneto-crystalline anisotropy (MCA) as well as for calculations of the MCA constants. In particular, the dependence of the induced magnetic torque on different types of atomic displacements is analyzed.