Emergent Anomalous and Topological Hall Responses in an Epitaxial Ferromagnetic Weyl Nodal-Line metal Fe5Si3

TL;DR

This study combines theoretical and experimental approaches to demonstrate that epitaxial Fe5Si3 thin films are a magnetic Weyl nodal-line material exhibiting topological Hall effects, large anomalous Hall conductivity, and chiral spin textures, advancing topological spintronics.

Contribution

It is the first comprehensive demonstration of Fe5Si3 as a magnetic Weyl nodal-line material with observed topological transport phenomena in epitaxial thin films.

Findings

Fe5Si3 hosts six pairs of Weyl nodes near the Fermi level.

Epitaxial Fe5Si3 exhibits a large anomalous Hall conductivity of 504 S/cm.

A substantial topological Hall resistivity of 1.6 μΩ·cm was observed across a wide temperature range.

Abstract

The interplay between real and reciprocal space topology yields intrinsically linked transport phenomena in magnetic Weyl systems, wherein the broken time-reversal symmetry, strong Dzyaloshinskii-Moriya interaction, and pronounced uniaxial anisotropy stabilize the momentum-space Berry-curvature monopoles (Weyl nodes) and real-space chiral spin textures. We present a combined first-principles and experimental study of epitaxial Fe5Si3 thin films, establishing them as a magnetic Weyl nodal-line material. First-principles Density Functional Theory (DFT) calculations unambiguously reveal that Fe5Si3 hosts a topologically nontrivial electronic structure containing six pairs of Weyl nodes at or near the Fermi level, accompanied by pronounced Berry curvature at high-symmetry points of the Brillouin Zone. High-quality epitaxial films exhibit robust ferromagnetism with a Curie temperature of ~370 K and strong magneto crystalline anisotropy. The magneto transport measurements on epitaxial films reveal the corresponding Berry curvature-driven responses, including a significantly large intrinsic anomalous Hall conductivity of 504 S/cm and a high anomalous Hall angle of 5.5%, which is in good agreement with DFT calculations. A negative and non-saturating longitudinal magnetoresistance is observed, consistent with a chiral-anomaly contribution from Weyl fermions near the Fermi level (EF). Furthermore, a substantial topological Hall resistivity of 1.6 {\mu}{\Omega} cm robust across a wide temperature range, indicating the possibility of robust chiral spin textures in the thin-film geometry. These combined theoretical and experimental results establish Fe5Si3 as a unique, low-cost, centrosymmetric magnetic Weyl nodal-line material, providing a versatile platform for exploring coupled real and reciprocal space topologies in topological spintronic applications.