Density-functional studies of the electronic structure of the perovskite oxides: La1-xCaxMnO3

Using density-functional methods, we study the electronic structures of the lanthanum-based open-quote open-quote double-exchange close-quote close-quote perovskite magnets. Antiferromagnetic insulating solutions are obtained for both the end members, LaMnO3 and CaMnO3, within the local density approximation (LDA), with the Jahn-Teller (JT) distortion of the oxygen octrahedron taken into account. The JT distortion splits off the Mn(3d)eg bands producing an energy gap within the LDA, with the bands derived from the (z2-1) orbital, pointed along the long basal-plane Mn emdash O bond, occupied and the (x2-y2) bands empty. The on-site Coulomb repulsion and the intra-site exchange terms are found to be, respectively, U≅8 endash 10 eV and J≅0.9 eV, from the open-quote open-quote constrained close-quote close-quote density-functional theory. The large value of U as compared to the bandwidth indicates that the manganese perovskite oxides are strongly correlated systems. copyright 1996 American Institute of Physics