Electronic structure of Nd1 xYxMnO3 from Mn K edge absorption spectroscopy and DFT methods
Résumé
The electronic structure of Nd1 xYxMnO3 (x=0-0.5) is studied using x-ray absorption near-edge structure (XANES) spectroscopy at the Mn K-edge along with the DFT-based LSDA+U and real space cluster calculations.The main edge of the spectra does not show any variation with doping. The pre-edge shows two distinct features which appear well-separated with doping.The intensity of the pre-edge decreases with doping. The theoretical XANES were calculated using real space multiple scattering methods which reproduces the entire experimental spectra at the main edge as well as the pre-edge. Density functional theory calculations are used to obtain the Mn4p, Mn3d and O2p density of states. For x = 0, the site-projected density of states at 1.7 eV above Fermi energy shows a singular peak of unoccupied eg (spin-up) states which is hybridized Mn4p and O2p states. For x = 0.5, this feature develops at a higher energy and is highly delocalized and overlaps with the 3d spin-down states which changes the pre-edge intensity. The Mn 4p DOS for both compositions, show considerable difference between the individual px, py and pz states. For x = 0.5, there is a considerable change in the 4p orbital polarization suggesting changes in the Jahn-Teller effect with doping.