Sub-domain structure in a single crystal of the magnetic topological insulator MnSb2Te4

TL;DR

This study investigates the hierarchical magnetic domain structure of MnSb2Te4 single crystals, revealing weakly coupled surface and bulk subsystems influenced by defects and surface symmetry breaking, using high-resolution imaging and magnetotransport measurements.

Contribution

It provides the first detailed characterization of the sub-domain structure in MnSb2Te4, linking it to defect distribution and surface effects.

Findings

Hierarchical domain structure with two spatial scales

Existence of weakly coupled surface and bulk magnetic subsystems

Correlation between defect distribution and domain formation

Abstract

The domain structure of a MnSb$_2$Te$_4$ single crystal with a Curie temperature $T_C \approx 45~K$ was studied using the high-resolution Bitter decoration technique. Magnetotransport measurements confirm a soft ferromagnetic ordering with a coercive field of $ \sim 100$ Oe. We revealed the formation of a hierarchical domain structure characterized by two distinct spatial scales. These results indicate the existence of two magnetically weakly coupled subsystems -- surface and bulk. The observed sub-domain structure can be attributed to the formation of a ferromagnetic well due to an inhomogeneous distribution of $\mathrm{Mn_{Sb}}$ antisite defects, with an additional contribution from symmetry breaking in the near-surface layer.