Persistence of magnetic moments at high density in disordered systems near the metal insulator transition

Spontaneous moment formation has been observed in disordered narrow band systems like doped semiconductors, or the liquid alloy Cs-Au. A recent model has provided a natural origin for this behaviour in a disordered system whenever the conduction band is almost empty. The intimate interplay between correlation, localization and magnetic properties characterizes this regime, and makes it different from the usual half filled band correlated system. In this work we investigate the behaviour of the model at high density. Precisely correlation effects are strongly enhanced in the limit of low filling of the band, giving rise to persistent local moments even at high density. Conversely in the well studied case of a half filled band local nioments vanish at high density, and correlation effects become negligible in this limit. At the light of the model we argue that the observed magnetic properties should persist at higher densities provided that only a few per cent electrons populate the conduction band.