DENSITY-FUNCTIONAL STUDIES OF THE ELECTRONIC-STRUCTURE OF THE PEROVSKITE OXIDES - LA1-XCAXMNO3

Using density-functional methods, we study the electronic structures o f the lanthanum-based ''double-exchange'' perovskite magnets. Antiferr omagnetic 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 a ccount. The JT distortion splits off the Mn(3d)e(g) bands producing an energy gap within the LDA, with the bands derived from the a (z(2)-1) orbital, pointed along the long basal-plane Mn-O bond, occupied and t he (x(2)-y(2)) bands empty. The on-site Coulomb repulsion and the intr a-site exchange terms are found to be, respectively, U similar or equa l to 8-10 eV and J similar or equal to 0.9 eV, from the ''constrained' ' density-functional theory. The large value of U as compared to the b andwidth indicates that the manganese perovskite oxides are strongly c orrelated systems. (C) 1996 American Institute of Physics.