Spin-lattice couplings in $3d$ ferromagnets: analysis from first-principles

TL;DR

This paper investigates exchange-mediated spin-lattice coupling in 3d ferromagnets using a simplified first-principles approach, revealing how these interactions vary with temperature, pressure, and symmetry, and connecting atomistic parameters to phenomenological models.

Contribution

It introduces a simplified atomistic method to analyze exchange-mediated magnetoelastic parameters in 3d ferromagnets, clarifying their behavior and relation to symmetry and experimental conditions.

Findings

Significant modifications in Dzyaloshinskii-Moriya interactions in Fe at ~100 K.

Minimal configuration dependence of interactions in Co and Ni.

Changes in magnetoelastic constants in Fe under isotropic contraction.

Abstract

Magnetoelasticity plays a crucial role in numerous magnetic phenomena, including magnetocalorics, magnon excitation via acoustic waves, and ultrafast demagnetization/Einstein-de Haas effect. Despite a long-standing discussion on anisotropy-mediated magnetoelastic interactions of relativistic origin, the exchange-mediated magnetoelastic parameters within an atomistic framework have only recently begun to be investigated. As a result, many of their behaviors and values for real materials remain poorly understood. Therefore, by using a proposed simple modification of the embedded cluster approach that reduces the computational complexity, we critically analyze the properties of exchange-mediated spin-lattice coupling parameters for elemental $3d$ ferromagnets (bcc Fe, fcc Ni, and fcc Co), comparing methods used for their extraction and relating their realistic values to symmetry considerations and orbitally-decomposed contributions. Additionally, we investigate the effects of noncollinearity (spin temperature) and applied pressure on these parameters. For Fe, we find that single-site rotations, associated with spin temperatures around $\sim100$ K, induce significant modifications, particularly in Dzyaloshinskii-Moriya-type couplings; in contrast, such interactions in Co and Ni remain almost configuration independent. Moreover, we demonstrate a notable change in the exchange-mediated magnetoelastic constants for Fe under isotropic contraction. Finally, the conversion between atomistic, quantum-mechanically derived parameters and the phenomenological magnetoelastic theory is discussed, which can be an useful tool towards larger and more realistic dynamics simulations involving coupled subsystems.