Large anomalous Hall effect in spin fluctuating devil’s staircase

Electrons in metals can show a giant anomalous Hall effect (AHE) when interacting with characteristic spin texture. The AHE has been discussed in terms of scalar-spin-chirality (SSC) in long-range-ordered noncollinear spin textures typified by Skyrmion. The SSC becomes effective even in the paramagnetic state with thermal fluctuations, but the resultant AHE has been limited to be very small. Here, we report the observation of large AHE caused by the spin fluctuation near the devil’s staircase transition in a collinear antiferromagnetic metal SrCo₆O₁₁. The AHE is prominent near and above the transition temperature at moderate magnetic fields, where the anomalous Hall angle becomes the highest level among known oxide collinear ferromagnets/antiferromagnets (>2%). Furthermore, the anomalous Hall conductivity is quadratically scaled to the conductivity. These results imply that the thermally induced solitonic spin defects inherent to the devil’s staircase transition promote SSC-induced skew scattering.