Unconventional anomalous Hall effect in a triangular lattice antiferromagnet

We studied the electrical transport properties of a classical spin triangular lattice antiferromagnet ${\mathrm{Ag}}_2{\mathrm{CrO}}_2$. In this material, a unique spin structure with a five-sublattice unit cell emerges below the Néel temperature $T_{\mathrm{N}}$, owing to frustration from strong further-neighbor interactions. The material also exhibits unique electrical transport properties coupled with its magnetism, due to a highly conductive layer of ${\mathrm{Ag}}_2$. Here, we report magnetoresistance and the Hall effect in ${\mathrm{Ag}}_2{\mathrm{CrO}}_2$ flake devices below and above $T_{\mathrm{N}}$ up to a magnetic field of 8 T. A large magnetoresistance and anomalous Hall effect were observed in the vicinity of $T_{\mathrm{N}}$, indicating that the fluctuation of the magnetic moments plays a key role. We propose possible scenarios in which the anomalous Hall effect is enhanced through thermal fluctuation.