Electronic structure study of the magnetoresistance material CaCu3Mn4O12 by LSDA and LSDA+U

The electronic structure of the large low-field magnetoresistance material CaCu3Mn4O12 is calculated by using the local-spin-density approximation (LSDA) and on-site-Coulomb interaction correction (LSDA+U) to;he 3d electronic states of Cu and Mn ions. The results obtained suggest a strong ionic character of this material despite a presence of a partial Mn-O covalence, effect. Three Cu ions per formula cell have their respective half-filled orbitals d(xy), d(yz), and d(xz) due to their different local crystal environments. Four Mn ions per;formula cell have nearly the same oxygen coordinations, As a consequence, the spin-up t(2g)-like orbitals (d(xy),d(yz), and d(xz)) are almost full-filled, while the spin-up e(g)-like orbitals (d(3z2-r2) and d(x2-y2)) are partially occupied due to a finite pd hybridization. And it is shown that the sublattices of Cu ions and Mn ones are both aligned in ferromagnetic order, while these two sublattices are coupled antiferromagnetically, thus giving a net spin moment of 9 mu(B) per formula. The LSDA+U calculation yields a semiconducting solution, which is improved upon a half-metallic state given by the LSDA calculation and consistent with an experimental measurement.