Spin-polarized imaging of the antiferromagnetic structure and field-tunable bound states in kagome magnet FeSn

TL;DR

This study uses spin-polarized scanning tunneling microscopy to reveal the antiferromagnetic surface structure of FeSn, showing robust electronic states against magnetic fields but impurity-bound states that are field-tunable, advancing understanding of kagome magnets.

Contribution

First atomic-scale visualization of FeSn's layered antiferromagnetic structure and analysis of impurity-bound states, highlighting their field-tunability and magnetic coupling.

Findings

Atomic-scale antiferromagnetic surface structure revealed.

Electronic density-of-states is insensitive to external magnetic fields.

Impurity-bound states exhibit strong coupling to magnetic fields.

Abstract

Kagome metals are as an exciting playground for the explorations of novel phenomena at the intersection of topology, electron correlations and magnetism. The family of FeSn-based kagome magnets in particular attracted a lot of attention for simplicity of the layered crystal structure and tunable topological electronic band structure. Despite a significant progress in understanding their bulk properties, surface electronic and magnetic structures are yet to be fully explored in many of these systems. In this work, we focus on a prototypical kagome metal FeSn. Using a combination of spin-averaged and spin-polarized scanning tunneling microscopy, we provide the first atomic-scale visualization of the layered antiferromagnetic structure at the surface of FeSn. In contrast to the field-tunable electronic structure of cousin material Fe3Sn2 that is a ferromagnet, we find that electronic density-of-states of FeSn is robust to the application of external magnetic field. Interestingly, despite the field-insensitive electronic band structure, FeSn exhibits bounds states tied to specific impurities with large effective moments that strongly couple to the magnetic field. Our experiments provide microscopic insights necessary for theoretical modeling of FeSn and serve as a spring board for spin-polarized measurements of topological magnets in general.