Field dependence of the anomalous Hall effect coefficient of granular alloys with giant magnetoresistance

It is shown theoretically that the anomalous Hall effect (AHE) coefficient R-s of magnetic granular alloys exhibiting giant magnetoresistance (GMR) depends strongly and, in the general case, nonmonotonically on the magnetic field as a result of the effect of the field on the character of the charge-carrier scattering and the AHE. The experimental data, presented by H. Sate, H. Hemmi, Y. Kobayashi et al., J. Appl. Phys. 76, 6919 (1994), on the field dependence R-s(H) in Co-Ag granular alloys at low temperatures are explained. The presence of a maximum in the field dependence /R-s(H)/ in annealed Co-Ag alloys attests to the fact that skew scattering plays a dominant role in the formation of the AHE and that the main carriers of the AHE in these alloys are states whose spin polarization is directed oppositely to the magnetization. The presence of a minimum in this dependence for unannealed samples indicates nonuniformity of the granule size distribution. (C) 1997 American Institute of Physics.