Ab initio calculation of charge- and spin-controlled Sr1-x-yLax+yTi1-xCrxO3

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 Sri(-x-y)La(x+y)Ti(1-x)Cr(x)O(3) In this paper, we present an ab initio calculation of the electronic structure of Sr1-x,La--y(x),Ti1-x,CrxO3 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. (c) 2006 Elsevier B.V. All rights reserved.