Evolution of electronic and magnetic properties in Mn- and Co-alloyed ferromagnetic kagome metal Fe3Sn2

TL;DR

This study investigates how alloying Fe3Sn2 with Mn and Co affects its electronic and magnetic properties, revealing Mn can effectively tune the Fermi level and preserve ferromagnetism, unlike Co which leads to phase separation.

Contribution

It demonstrates that Mn alloying in Fe3Sn2 can tune the Fermi level while maintaining crystalline quality and ferromagnetism, providing a new way to control kagome metal properties.

Findings

Mn alloying shifts the Fermi level consistent with hole-doping

Fe3-xMnxSn2 retains room temperature ferromagnetism

Co alloying results in phase separation and does not incorporate into the structure

Abstract

Kagome metals are an intriguing class of quantum materials as the presence of both flat bands and Dirac points provides access to functional properties present in strongly correlated and topological materials. To fully harness these electronic features, the ability to tune the Fermi level relative to the band positions is needed. Here we explore the structural, electronic and magnetic impacts of substitutional alloying within ferromagnetic kagome metal Fe3Sn2 in thin films grown by molecular beam epitaxy. Transition metals Mn and Co are chosen as substitutes for Fe to reduce or increase the d-band electron count, thereby moving the Fermi level accordingly. We find that Co is not incorporated into the Fe3Sn2 structure but instead results in a two-phase Fe-Co and (Fe,Co)Sn composite. In contrast, Fe3-xMnxSn2 films are realized with x up to 1.0, retaining crystalline quality comparable to the parent phase. The incorporation of Mn repositions the flat bands relative to the Fermi level in a manner consistent with hole-doping, as revealed by hard x-ray photoemission and density functional theory. The Fe3-xMnxSn2 films retain room temperature ferromagnetism, with x-ray magnetic circular dichroism measurements confirming that the Fe and Mn moments are ferromagnetically aligned. The ability to hole-dope this magnetic kagome metal provides a platform for tuning properties such as anomalous Hall and Nernst responses.