The role of Coulomb correlation in magnetic and transport properties of doped manganites: La_0.5Sr_0.5MnO₃ and LaSr₂Mn₂O₇

Results of local spin-density approximation (LSDA) and LSDA+U calculations of the electronic structure and magnetic configurations of the 50% hole-doped pseudocubic perovskite La_0.5Sr_0.5MnO₃ and double-layered LaSr₂Mn₂O₇ are presented. We demonstrate that the on-site Coulomb correlation (U) of Mn d electrons has a very different influence on the (i) band structures, (ii) magnetic ground states, (iii) interlayer exchange interactions, and (iv) anisotropy of the electrical transport in these two manganites. A p-d hybridization analysis is employed to look for possible explanations for the LSDA failing to predict the observed magnetic and transport properties of the double-layered compound - in contrast to the case for the doped perovskite manganite.