Meta-magnetism of weakly-coupled antiferromagnetic topological insulators

TL;DR

This study investigates the magnetic phase transitions in van der Waals topological insulators MnBi2Te4 and MnBi4Te7, revealing how inter-layer exchange coupling influences magnetic order and can induce a transition from antiferromagnetic to ferromagnetic-like states.

Contribution

It introduces a bi-layer Stoner-Wohlfarth model to describe the magnetic transition driven by the ratio of inter-layer exchange to anisotropy in these materials.

Findings

Transition from A-type antiferromagnetic to ferromagnetic-like state controlled by J/K ratio.

Angular dependence of spin-flop and switching fields characterized.

Model successfully describes magnetic behavior observed in experiments.

Abstract

The magnetic properties of the van der Waals magnetic topological insulators MnBi$_2$Te$_4$ and MnBi$_4$Te$_7$ are investigated by magneto-transport measurements. We evidence that the relative strength of the inter-layer exchange coupling J to the uniaxial anisotropy K controls a transition from an A-type antiferromagnetic order to a ferromagnetic-like metamagnetic state. A bi-layer Stoner-Wohlfarth model allows us to describe this evolution, as well as the typical angular dependence of specific signatures, such as the spin-flop transition of the uniaxial antiferromagnet and the switching field of the metamagnet.