Electronic structure and magnetic properties of hole-carrier-doped La ₂ MnNiO₆:La_2-x Sr_x MnNiO₆

We have investigated hole-carrier-doping effects in a ferromagnetic insulator La₂ MnNiO₆. Employing the ab initio band-structure method, we have examined the changes in the electronic structures and the valence states of Sr-doped La_2-x Sr_x MnNiO ₆ with varying Sr doping ratio. On Sr doping, we have found a transition from a ferromagnetic insulating phase to a half-metallic phase. The half-metallic nature in La_2-x Sr_x MnNiO₆ is found to be robust with respect to the on-site Coulomb correlation of transition metal 3d electrons and the antisite disorder at B sites. We have corroborated that the substantially weak x-ray magnetic circular dichroism signal observed for La_2-x Sr_x MnNiO₆, as compared to the undoped system, is caused by antisite disorder at B sites in a Sr-doped system.