Anatomy of anomalous Hall effect due to magnetic fluctuations

TL;DR

This paper investigates how magnetic fluctuations affect the interpretation of the anomalous Hall effect (AHE), especially distinguishing intrinsic topological contributions from fluctuation-induced signals, using PrAlGe as a case study.

Contribution

It demonstrates that magnetic fluctuations complicate the identification of intrinsic AHE, providing a combined experimental approach to clarify the AHE's origin in topological materials.

Findings

Magnetic fluctuations can mimic intrinsic AHE signals.

PrAlGe shows different AHE behavior below and above ferromagnetic transition.

Insights applicable to Kagome metals and transition metal dichalcogenides.

Abstract

The anomalous Hall {\color{black} e}ffect (AHE) has emerged as a key indicator of time-reversal symmetry breaking (TRSB) and topological features in electronic band structures. Absent of a magnetic field, the AHE requires spontaneous TRSB but has proven hard to probe due to averaging over domains. The anomalous component of the Hall effect is thus frequently derived from extrapolating the magnetic field dependence of the Hall response. We show that discerning whether the AHE is an intrinsic property of the field free system becomes intricate in the presence of strong magnetic fluctuations. {\color{black}As a study case,} we use the Weyl semimetal PrAlGe, where TRSB can be toggled via a ferromagnetic transition, providing a transparent view of the AHE's topological origin. Through a combination of thermodynamic, transport and muon spin relaxation measurements, we contrast the behaviour below the ferromagnetic transition temperature to that of strong magnetic fluctuations above. Our results {\color{black}on PrAlGe provide general insights into the} interpretation of anomalous Hall signals in systems where TRSB is debated, such as families of Kagome metals or certain transition metal dichalcogenides.