Butterfly-shaped magnetoresistance in triangular-lattice antiferromagnet Ag$_2$CrO$_2$

TL;DR

This study reports a unique butterfly-shaped magnetoresistance in a triangular-lattice antiferromagnet Ag$_2$CrO$_2$, linked to spin fluctuations and anisotropy, with potential implications for spintronic devices.

Contribution

It introduces the observation of butterfly-shaped MR in Ag$_2$CrO$_2$ and proposes a theoretical model involving spin fluctuations and Ising anisotropy.

Findings

Butterfly-shaped MR appears only with magnetic field perpendicular to CrO$_2$ plane.

Maximum MR ratio of approximately 15% at the magnetic ordering temperature.

Distinct from conventional magnetic materials' MR behavior.

Abstract

Spintronic devices using antiferromagnets (AFMs) are promising candidates for future applications. Recently, many interesting physical properties have been reported with AFM-based devices. Here we report a butterfly-shaped magnetoresistance (MR) in a micrometer-sized triangular-lattice antiferromagnet Ag$_2$CrO$_2$. The material consists of two-dimensional triangular-lattice CrO$_2$ layers with antiferromagnetically coupled $S$ = 3/2 spins and Ag$_2$ layers with high electrical conductivity. The butterfly-shaped MR appears only when the magnetic field is applied perpendicularly to the CrO$_2$ plane with the maximum MR ratio ($\approx$ 15%) at the magnetic ordering temperature. These features are distinct from those observed in conventional magnetic materials. We propose a theoretical model where fluctuations of partially disordered spins with the Ising anisotropy play an essential role in the butterfly-shaped MR in Ag$_2$CrO$_2$.