On the competition between magnetic order and local Kondo effect in Kondo lattice

We investigate the competition between magnetic order and local Kondo effect in a Kondo lattice model (i.e. the Coqblin-Schrieffer Hamiltonian extended to a lattice) in a mean-field approximation, taking account of the spin-orbit degeneracy N <Subscript>s.o.</Subscript> of each localized f level. This leads to the definition of a N <Subscript>s.o.</Subscript> dependent Kondo temperature. We study the Kondo phase and compare its energy with the energies of magnetic phases, when the number of the conduction band electron per site is near one. We present a phase diagram which shows the occurrence of three phases: Kondo, antiferromagnetic and paramagnetic phases. Our model in the mean-field approximation also shows a somewhat flat Kondo temperature, for large values of N <Subscript>s.o.</Subscript>, as a function of the exchange coupling J between conduction and localized f electrons. Finally we show some scaling effects between N <Subscript>s.o.</Subscript> and J and we define a corresponding Kondo temperature. Copyright Società Italiana di Fisica, Springer-Verlag 1999