Fe-Sn nanocrystalline films for flexible magnetic sensors with high thermal stability

TL;DR

This paper demonstrates that Fe-Sn nanocrystalline films exhibit a large anomalous Hall effect suitable for flexible, thermally stable magnetic sensors, with potential for new device applications based on kagome metals.

Contribution

It introduces Fe-Sn nanocrystalline films with enhanced anomalous Hall effect and demonstrates their application in flexible, thermally stable magnetic sensors.

Findings

Large anomalous Hall effect observed in Fe-Sn nanocrystalline films.

Films show high thermal stability and mechanical flexibility.

Optimal composition close to Fe3Sn2 enhances Hall angle.

Abstract

The interplay of magnetism and spin-orbit coupling on an Fe kagome lattice in Fe3Sn2 crystal produces a unique band structure leading to an order of magnitude larger anomalous Hall effect than in conventional ferromagnetic metals. In this work, we demonstrate that Fe-Sn nanocrystalline films also exhibit a large anomalous Hall effect, being applicable to magnetic sensors that satisfy both high sensitivity and thermal stability. In the films prepared by a co-sputtering technique at room temperature, the partial development of crystalline lattice order appears as nanocrystals of Fe-Sn kagome layer. The tangent Hall angle, the ratio of Hall resistivity to longitudinal resistivity, is largely enhanced in the optimal alloy composition of close to Fe3Sn2, exemplifying the kagome origin even though the films are composed of nanocrystal and amorphous-like domains. These ferromagnetic Fe-Sn films possess great advantages as a Hall sensor over semiconductors in thermal stability owing to the weak temperature dependence of the anomalous Hall responses. Moreover, the room-temperature fabrication enables us to develop a mechanically flexible Hall sensor on an organic substrate. These demonstrations manifest the potential of kagome metal as an untapped reservoir for designing new functional devices.