Giant anomalous Hall effect in a spin orbit coupled ferromagnet MnBi

Large anomalous Hall effects (AHE) on the order of 10³ Scm^-1 have been found in various ferromagnets, mainly originating from intrinsic Berry curvature with the broken time reversal symmetry. However, further enhancement has rarely been reported, which is limited by the nature of the intrinsic mechanism. Extrinsic effects, particularly the skew scattering, promise higher AHE beyond 10⁴ Scm^-1 but requires high electrical conductivity that few ferromagnets satisfy. In this presentation, we report the giant AHE and anomalous Nernst effect (ANE) in a simple binary ferromagnet MnBi. High quality single crystals with high longitudinal electrical conductivity over 3×10⁶ Scm^-1 are for the first time achieved, which satisfies the skew scattering criterion. Thanks to the large spin-orbit coupling from Bi, the observation of a pure skew scattering AHE signal below is observed below 10 K, with an AHE conductivity orders of magnitude higher than the Berry curvature originated AHE, with a profound anomalous Nernst conductivity over 100 AK^-1m^-1. We highlight that the role of skew scattering mechanism in enhancing the AHE and ANE for highly conductive spin orbit coupled ferromagnets.