Ab initio calculation of charge- and spin-controlled Sr_1-x-yLa_x+yTi_1-xCr_xO₃

Perovskite SrTiO₃ is a wide-gap band insulator. Because of the stability of its crystal structure, various nonmagnetic and magnetic atoms can be doped into the A-site and the B-site, respectively. A-site substitution, namely La³⁺ for Sr²⁺, introduces free electrons in the conduction band, while B-site substitution, namely Cr³⁺ for Ti⁴⁺, introduces not only localized spins but also free holes in the valence band. Therefore, we can independently introduce x localized spins and y free electrons (or holes) in SrTiO₃ by co-doping La and Cr, by the composition Sr_1-x-yLa_x+yTi_1-xCr_xO₃. In this paper, we present an ab initio calculation of the electronic structure of Sr_1-x-yLa_x+yTi_1-xCr_xO₃ by the KKR-CPA-LDA method, changing the doping concentrations x and y systematically within 0<x<0.2 and -0.2<y<0.2. We found that the Cr t_2g-states are well localized, and due to the large exchange splitting, only the majority spin states are occupied. However, the energy of the occupied Cr t_2g-states are considerably shallow compared to the photoemission experiment, suggesting the importance of the electron correlation for these localized states. The total magnetic moment is almost proportional to the Cr concentration as expected; however, it considerably changes with La concentration.