A theoretical study of the cluster glass-Kondo-magnetic disordered alloys

Abstract

Abstract The physics of disordered alloys, such as typically the well known case of CeNi 1 - x Cu x alloys, showing an interplay among the Kondo effect, the spin glass state and a magnetic order, has been studied firstly within an average description like in the Sherrington–Kirkpatrick model. Recently, a theoretical model [S.G. Magalhaes, F.M. Zimmer, P.R. Krebs, B. Coqblin, Phys. Rev. B 74 (2006) 014427] involving a more local description of the intersite interaction has been proposed to describe the phase diagram of CeNi 1 - x Cu x . This alloy is an example of the complex interplay between Kondo effect and frustration in which there is in particular the onset of a cluster-glass state. Although the model given in Magalhaes et al. [Phys. Rev. B 74 (2006) 014427] has reproduced the different phases relatively well, it is not able to describe the cluster-glass state. We study here the competition between the Kondo effect and a cluster glass phase within a Kondo-lattice model with an inter-cluster random Gaussian interaction. The inter-cluster term is treated within the cluster mean-field theory for spin glasses [C.M. Sokoulis, Phys. Rev. B 18 (1978) 3757], while, inside the cluster, an exact diagonalisation is performed including inter-site ferromagnetic and intra-site Kondo interactions. The cluster glass order parameters and the Kondo correlation function are obtained for different values of the cluster size, the intra-cluster ferromagnetic coupling and the Kondo intra-site coupling. We obtain that the increase of the Kondo coupling tends clearly to destroy the cluster glass phase.