Pseudogap formation and coexistence of localised and extended states in disordered transition metal alloys

Abstract

The model of electron structure of Ti-based 3d metal alloys is proposed on the basis of the analysis of their electron properties. It includes the formation of the impurity d band almost non-hybridised with the conductivity electron states of Ti and the Mott-Hubbard transition in the former at some critical impurity concentration xc. It is shown that a pseudogap occurs in the conductivity band of the host near the Fermi energy as result of this transition. The experimental study of the concentration dependence of the conductivity sigma indicates the tendency of the host electron states to the Anderson localisation when x to xc which agrees with the conclusion of the model. At x>or approximately=xc the observed dependence of sigma on the temperature and magnetic field show the coexistence of extended and localised states near the Fermi level. The peculiarities of the physical properties of alloys with x approximately=xc and the nature of the anomalous magnetoresistance near the metal-insulator transition are discussed.