Unexpected Anisotropic Mn-Sb Anti-site Distribution and Van der Waals Epitaxy of MnSb2Te4

TL;DR

This paper uncovers unexpected uneven anti-site distribution in MnSb2Te4, revealing a reduced-symmetry structure with potential for novel topological and magnetic properties, and introduces a Van der Waals epitaxy method for thin film growth.

Contribution

It demonstrates the first observation of anisotropic anti-site distribution and develops a Van der Waals epitaxy technique for MnSb2Te4 thin films.

Findings

Uneven anti-site distribution confirmed by electron microscopy.

Successful Van der Waals epitaxy of MnSb2Te4 over Sb2Te3 seeds.

Potential for integrating MnSb2Te4 into Si-based devices.

Abstract

Mn-Sb site mixing directly impacts both the magnetic and topological properties of MnSb2Te4. This study reveals, unlike previously believed, that these anti-sites can be unevenly distributed within the crystal. To that end, a polycrystalline sample was created with a two-step synthesis using MnTe and Sb2Te3 as precursors. DC-SQUID magnetometry was used to confirm its magnetic properties. In addition, the use of High-Resolution Scanning Transmission Electron Microscopy combined with Energy-Dispersive X-ray Spectroscopy allowed us to identify the presence of an inversion-breaking asymmetry in the anti-site distribution. This reduced-symmetry structure bears resemblance to the recently proposed class of Janus materials and thus warrants further exploration due to its potential for combining topology and magnetism with other effects, such as non-linear optics and piezoelectricity. Finally, to further elucidate the interplay between site mixing, doping, topology, and magnetism, a method for growing MnSb2Te4 thin films over amorphous SiOx using Sb2Te3 seeds is introduced. The successful Van der Waals epitaxy of MnSb2Te4 over Sb2Te3 seeds using Pulsed Laser Deposition is confirmed using Scanning Transmission Electron Microscopy. This represents a crucial step in incorporating these materials into a Si-based architecture, which offers the possibility of controlling the Fermi lever via gating.