Extensions to the Kondo lattice model to achieve realistic Curie temperatures and appropriate behavior of the resistivity for manganites

Abstract

We investigate the influence of the Jahn-Teller distortion and a direct antiferromagnetic moment coupling as extensions to a two-band Kondo lattice model for the magnetic and electronic properties of manganites. Those are calculated self-consistently via an interpolating self-energy model and a modified RKKY technique using finite Hund coupling and quantum spins. We found that both effects are essential to achieve realistic Curie temperatures if we regard intraband Coulomb repulsion. Using reliable model parameters we got results which are in very good agreement with experimental data in the whole ferromagnetic doping range. In the calculated phase diagram there are ferromagnetic metal to paramagnetic insulator transitions, accompanied by a Colossal Magnetoresistance (CMR) behavior. To improve the comparability of the measured behavior of the resistivity with the calculated one, we have to switch on interband Coulomb correlations.