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

We investigate the competition between magnetic order and local Kondo effec t in a Kondo lattice model (i.e. the Coqblin-Schrieffer Hamiltonian extende d to a lattice) in a mean-field approximation, taking account of the spin-o rbit degeneracy N-s.o. of each localized f level. This leads to the definit ion of a N-s.o. dependent Kondo temperature. We study the Kondo phase and c ompare 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 diagr am 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-s.o., as a functio n of the exchange coupling J between conduction and localized f electrons. Finally we show some scaring effects between N-s.o. and J and we define a c orresponding Kondo temperature.