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

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${}_2$.

25 pages, 6 figures

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