The anomalous Hall effect is an intriguing variant of the ordinary Hall effect, in which a magnetic field applied through a conductor causes a voltage to arise perpendicular to it. For ferromagnets, the magnetization of the conductor causes another contribution to the Hall effect, larger than the ordinary Hall effect, hence the anomaly. The effect is too big to be the simple result of the addition of the magnetization to the applied magnetic field, and the debate continues regarding the cause of the anomalous Hall effect in ferromagnetic materials. Recent experimental and theoretical works show that the anomalous Hall effect is mostly caused by the Berry phase of band electrons.
In a paper published in Physical Review B, Yuki Shiomi, Yoshinori Onose, and Yoshinori Tokura of the University of Tokyo, Japan, have investigated the effect of scattering on the intrinsic anomalous Hall effect in iron, nickel, and cobalt, and their related alloys. They separate out the regular Hall effect from its anomalous counterpart and find the transition from scattering-dependent to scattering-free behavior with decreasing resistivity. The results indicate that the Berry phase induced anomalous Hall effect is not affected by scattering in clean samples. – Daniel Ucko