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 (LS DA) 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 char acter of this material despite a presence of a partial Mn-O covalence, effe ct. Three Cu ions per formula cell have their respective half-filled orbita ls d(xy), d(yz), and d(xz) due to their different local crystal environment s. 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) an d 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 f erromagnetic order, while these two sublattices are coupled antiferromagnet ically, thus giving a net spin moment of 9 mu(B) per formula. The LSDA+U ca lculation yields a semiconducting solution, which is improved upon a half-m etallic state given by the LSDA calculation and consistent with an experime ntal measurement.