Temperature dependence of the intrinsic anomalous Hall effect in nickel

The unusual temperature dependence of the anomalous Hall effect (AHE) in Ni is investigated by an experimental approach which enables us to extract the intrinsic anomalous Hall conductivity over the whole temperature range. In stark contrast to the existing literature, the intrinsic contribution in Ni is found to be strongly temperature dependent between 5 and 150 K, where the corresponding magnetization remains almost unchanged. This pronounced temperature dependence, a cause of the long-standing confusion concerning the physical origin of the AHE in Ni, is likely due to the existence of small band gaps caused by the spin-orbit coupling at the Fermi level. Our result helps pave the way for the general claim of the Berry-phase interpretation for the AHE, and also points out another mechanism for the temperature dependence of the AHE.