Quantum Effects at a Spin-Flop Transition in the Antiferromagnetic Topological Insulator MnBi$_2$Te$_4$

TL;DR

This paper investigates quantum effects influencing the magnetization behavior at a spin-flop transition in the topological antiferromagnet MnBi₂Te₄, revealing how crystal field components affect magnetic properties and refining the material's spin model.

Contribution

It introduces a theoretical analysis linking quantum effects to magnetization features in MnBi₂Te₄ and refines the effective spin model parameters based on experimental data.

Findings

Quantum effects cause anomalous magnetization increases before and after the spin-flop transition.

The trigonal component of the crystal field significantly influences magnetic behavior.

Refined parameters of the effective spin model align with experimental observations.

Abstract

It is shown that the experimentally detected features in the low-temperature behavior of the magnetization in an external magnetic field perpendicular to the layers of manganese ions of the topological antiferromagnet MnBi$_2$Te$_4$ are due to quantum effects induced by the off-diagonal nature of the trigonal component of the crystal field. In this case, the anomalous increase in the magnetization of the material before the spin-flop transition, as well as after it in the phase of "collapsed" sublattices, is explained by the suppression of contributions from quantum effects. The comparison of the results of the theoretical analysis with experimental data has made it possible to refine the parameters of the effective spin model of MnBi$_2$Te$_4$ and to establish the important role of the noted trigonal component.