Magnetic Order and Strain in Hexagonal Manganese Pnictide CaMn$_2$Bi$_2$

TL;DR

This study explores the magnetic properties of CaMn₂Bi₂ using DFT with Hubbard U and spin-orbit coupling, revealing strain-tunable magnetic anisotropy and potential for spintronic applications.

Contribution

It provides a detailed theoretical analysis of magnetic interactions and strain effects in CaMn₂Bi₂, a promising magnetic material with tunable properties.

Findings

Magnetic interactions are accurately modeled by a modified Heisenberg model.

Magnetic anisotropy shows an easy plane with strain-dependent magnetization direction.

Strain can switch the preferred magnetization axis, enabling control over magnetic states.

Abstract

The manganese pnictide CaMn$_2$Bi$_2$, with Mn atoms arranged in a puckered honeycomb structure, exhibits narrow-gap antiferromagnetism, and it is currently a promising candidate for the study of complex electronic and magnetic phenomena, such as magnetotransport effects and potential spin spirals under high pressure. In this paper, we perform a detailed research of the magnetic properties of CaMn$_2$Bi$_2$ using density functional theory (DFT) combined with the Hubbard U correction and spin-orbit coupling, which accurately describe the magnetic interactions. Our results obtained for a large number of magnetic configurations are accurately captured by a modified Heisenberg model that includes on-site magnetization terms to describe magnetic energy excitations. We further investigate the role of the spin-orbit coupling, and find that the magnetic anisotropy of CaMn$_2$Bi$_2$ shows an easy plane, with the preferred magnetization direction being exchanged between axes in the plane by applying small strain values. This strain-tunable magnetization, driven by the interplay between spin-orbit interactions and lattice distortions, highlights the potential for controlling magnetic states in Mn-pnictides for future applications in spintronic and magnetoelectric devices.