Magnetic Phase Diagram of Mn3+xSn1-x Epitaxial Thin Films: Extending the Anomalous Hall Effect to Low Temperatures via Intrinsic Alloying

TL;DR

This study explores how intrinsic alloying in Mn3+xSn1-x epitaxial thin films tunes magnetic phase transitions, enabling the stabilization of the inverse triangular antiferromagnetic phase at very low temperatures and extending the material's topological properties.

Contribution

It demonstrates that Mn alloying in Mn3+xSn1-x thin films can systematically control magnetic phase transitions, particularly stabilizing the IT-AFM phase at cryogenic temperatures.

Findings

Intrinsic alloying with Mn stabilizes IT-AFM phase down to liquid helium temperatures.

A magnetic anomaly around 55 K below TN with thermal hysteresis was observed.

Lattice parameter changes correlate with the reduction of TN in thin films.

Abstract

Antiferromagnets with broken time-reversal symmetry, such as Mn3Sn, have emerged as promising platforms for exploring topological and correlated electron physics. Mn3Sn is known to show two magnetic phase transitions: a non-collinear inverse triangular antiferromagnetic (IT-AFM) spin configuration is formed below its Neel temperature, whereas at T1 that usually locates below room temperature, it transits to an incommensurate spin state. Accordingly, intriguing properties such as a strong anomalous Hall effect, observed from TN to T1, disappear below T1, limiting its utility at low temperatures. While bulk Mn3Sn has been extensively studied, the magnetic phase transitions and their tunability in thin films remain largely unexplored. Here, we investigate the magnetic and magneto-transport properties of Mn3+xSn1-x epitaxial thin films prepared by magnetron sputtering, systematically varying the Mn-Sn composition. Our results reveal that intrinsic alloying with Mn provides us with a handle to tune T1, with the IT-AFM phase stabilized down to liquid helium temperatures for x > 0.15. From a magnetic phase diagram for epitaxial thin films, we also find a consistent magnetic anomaly ~55 K below TN, accompanied by thermal hysteresis. Furthermore, the reduction of TN in thin films relative to bulk values is shown to correlate with lattice parameter changes. These findings extend the accessible temperature range for Mn3Sn's topological properties, paving the way for novel applications and further investigations into the interplay of spin, lattice, and electronic degrees of freedom in thin-film geometries.