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

TL;DR

This paper presents a theoretical study of the interplay between Kondo effect, cluster glass, and magnetic order in disordered alloys, using a cluster mean-field approach to better describe the complex phases.

Contribution

It introduces a cluster mean-field model for Kondo lattice alloys that captures the competition between Kondo screening and cluster glass formation, improving upon previous models.

Findings

Increasing Kondo coupling suppresses the cluster glass phase.

The model reproduces phase diagrams with multiple competing states.

Cluster size and intra-cluster interactions influence phase stability.

Abstract

The physics of disordered alloys, such as typically the well known case of CeNi1-xCux 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 (PRB 74, 014427 (2006)) involving a more local description of the intersite interaction has been proposed to describe the phase diagram of CeNi1-xCux. 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 Ref. PRB 74, 014427 (2006) 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, 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, for instance, that the increase of the Kondo coupling tends to destroy the cluster glass phase.