Eur. Phys. J. B 2, 11-16 (1998)
https://doi.org/10.1007/s100510050220

Ferromagnetic ground state in the Kondo lattice model

Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong

Corresponding author: ^a sshen@kkucc.hku.hk

Received: 10 September 1997
Revised: 15 October 1997
Accepted: 17 October 1997
Published online: 15 March 1998

Abstract

We present a series of rigorous examples of the Kondo lattice model that exhibit full ferromagnetism in the ground state. The models are defined in one-, two- and three-dimensional lattices, and are characterized by a range of hopping terms, specific electron filling, and large ferromagnetic coupling. Our examples show that a sufficient strong but finite exchange coupling between conduction electrons and localized spins could overcome the competition from mobility of a finite density of electrons and drive the system from a paramagnetic phase to a ferromagnetic phase. We also establish a relation of ferromagnetism between the Hubbard model and Kondo lattice model. Meanwhile some rigorous results on ferromagnetism in the corresponding Hubbard model are presented.