Role of covalency in the ground-state properties of perovskite ruthenates: A first-principles study using local spin density approximations

We investigate the electronic structure of SrRuO₃ and CaRuO₃ using full potential linearized augmented plane wave method within the local spin density approximations. The ferromagnetic ground state in SrRuO₃ could exactly be described in these calculations and the calculated spin magnetic moment is found to be close to the experimentally observed values. Interestingly, the spin polarized calculations for CaRuO₃ exhibit large spin moment as observed in the experiments but the magnetic ground state has higher energy than that in the nonmagnetic solution. Various calculations for different structural configurations indicate that Ca-O covalency plays the key role in determining the electronic structure and thereby the magnetic ground state in this system.