Unconventional Anomalous Hall Effect in the Metallic Triangular-Lattice Magnet PdCrO2

TL;DR

This study reports an unconventional anomalous Hall effect in PdCrO2, a triangular-lattice antiferromagnet, observed below 20 K, suggesting complex spin interactions beyond simple 120-degree order.

Contribution

The paper provides experimental evidence of UAHE in PdCrO2 and discusses conditions for its emergence within Berry-phase mechanisms, challenging conventional understanding.

Findings

UAHE observed below 20 K in PdCrO2

Deviation from conventional Hall behavior at T*

Discussion of Berry-phase mechanisms for UAHE

Abstract

We experimentally reveal an unconventional anomalous Hall effect (UAHE) in a quasi-two-dimensional triangular-lattice antiferromagnet PdCrO2. Using high quality single crystals of PdCrO2, we found that the Hall resistivity deviates from the conventional behavior below T* = 20 K, noticeably lower than TN = 37.5 K, at which Cr^{3+} (S=3/2) spins order in a 120 degree structure. In view of the theoretical expectation that the spin chirality cancels out in the simplest 120 degree spin structure, we discuss required conditions for the emergence of UAHE within Berry-phase mechanisms.