Butterfly-shaped magnetoresistance in triangular-lattice antiferromagnet Ag 2 CrO 2

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 (≈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 .