THE KONDO-LATTICE MODEL AND THE KONDO-SPIN GLASS COMPETITION IN HEAVY FERMION SYSTEMS

摘要

Many cerium or ytterbium alloys and compounds are characterized by heavy-fermion behavior due to the Kondo effect. In the case of a lattice, there is a strong competition between the Kondo effect and magnetic ordering. The magnetic order close to the quantum critical point(QCP) is generally an antiferromagnetic one, but could be also a ferromagnetic one or a spin-glass one in disordered systems. We review here the main features of the Kondo lattice model within a mean-field treatment of the Hamiltonian, including both the s-f exchange intra-site interaction and the nearest neighbor inter-site f-f interaction. First, we study the nonmagnetic case and discuss the effects of conduction band filling and of the inter-site exchange parameter on the occurrence of the Kondo effect and short-range magnetic correlations. Second, we treat the spin glass-Kondo competition by considering a random inter-site interaction and we study the competition between Kondo, spin-glass and ferromagnetic phases. The nature of the transition at the QCP is also discussed and comparison with experimental data in heavy fermions systems is finally presented.