Meta-magnetism of weakly-coupled antiferromagnetic topological insulators

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.

22 pages, 8 figures; typos corrected, references added