Structural and magnetic properties of co-sputtered epitaxial Fe-Sn kagome thin films

TL;DR

This study reports the successful growth and characterization of epitaxial Fe-Sn kagome thin films, revealing how phase composition influences magnetic properties, including a unique temperature-dependent coercivity in mixed phases.

Contribution

It introduces a method to produce and analyze epitaxial Fe-Sn kagome thin films with controlled phase content and links phase composition to magnetic behavior.

Findings

High-quality epitaxial Fe3Sn2 and FeSn films were grown on sapphire.

Magnetization correlates with phase content predicted from structural analysis.

Mixed-phase films exhibit unique temperature-dependent coercivity not seen in pure phases.

Abstract

In recent years the intermetallic alloys of Fe and Sn have gained significant interest due to a rich variety of magnetic properties present in these materials. The crystal Fe3Sn2 is a frustrated ferromagnet, while the crystallographically similar FeSn, which differs only by the stacking sequence of its Fe-containining kagome and stanene layers, is an antiferromagnet. Thin-film growth techniques such as magnetron sputtering allow for these different stoichiometric compositions to be grown through adjustments of the rate of deposition of the individual Fe and Sn sources, while all other conditions remain constant. Here, we report the production of high quality epitaxial thin films of Fe$_3$Sn$_2$ and FeSn on sapphire with a Pt seed layer, as well as a mixed phase containing intergrowths of both crystals, all of which we have characterized using both X-ray and four-dimensional scanning transmission electron microscopy (4D-STEM) methods. The resulting crystallographic phase content is compared to the results of magnetization measurements, with correspondence between the predicted ferromagnetic phase content and the resulting magnetization. Further magnetic properties of these films can then also be compared, leading to the discovery of a unique behavior in the temperature dependent coercivity within highly mixed phase alloys, a feature that is absent in either pure Fe3Sn2 and FeSn.