Ferromagnetism in the multiband Kondo lattice model

The ferromagnetic spin-exchange interaction between the itinerant electrons and localized moments on a periodic lattice, studied within the so-called Kondo lattice model, is considered for multiband situation where the hopping integral is a matrix in general. The modified Ruderman-Kittel-Kasuya-Yosida theory, wherein one can map such a model onto an effective Heisenberg-type system, is extended to a multiband case with finite bandwidth and hybridization on a simple-cubic lattice. As an input for the evaluation of the effective exchange integrals, one requires the multiband electronic self-energy, which is taken from an earlier proposed ansatz. Using the above procedure, we determine the magnetic properties of the system such as Curie temperature while calculating the chemical potential and magnetization within a self-consistent scheme for various values of system parameters. The results are discussed in detail and the model is motivated in order to study the electronic, transport, and magnetic properties of real materials like GdN.