A model for the behaviour of the Hall coefficient in amorphous and liquid transition metals

The Hall coefficient of many amorphous metal alloys composed of transition metals and ‘nearly-free-electron’-like metals is often positive in sign. We have argued previously that the effect of hybridization between free electrons and the d bands is precisely analogous to anomalous dispersion in optics and can give rise to an S-shaped dispersion relation familiar in the optical context. The existence of negative ‘group velocities’ defined by the slope of the dispersion curve has been put forward as the reason for positive Hall coefficients and calculations are presented here which put this idea on a much firmer footing, taking the strong ‘damping’ into account. Although the d states may contribute strongly to the ordinary conductivity, they should play a minor rôle in the Hall conductivity.