Relativistic many-electron calculations of Cr3+ L2,3-edge x ray absorption near-edge structures for Cr3+:α-Al2O3 and α-Cr2O3 and magnetic circular dichroism of Cr3+ L2,3-edge x ray absorption near-edge structures for Cr3+:α-Al2O3

We performed first-principles calculations for Cr3+ L-2,L-3-edge x ray absorption near-edge structures (XANES) of Cr3+:alpha-Al2O3 (ruby) and alpha-Cr2O3 and magnetic circular dichroism (MCD) of Cr3+ L-2,L-3-edge XANES of ruby using a relativistic multielectron method. In order to investigate the lattice relaxation effects for ruby, theoretical studies were carried out using the three types of model clusters, including the lattice relaxation effects. These theoretical XANES spectra for both ruby and alpha-Cr2O3 well reproduced the experimental XANES spectra. The lattice relaxation effects on the XANES spectra for ruby were very small, while the results of configuration analysis of the many-electron wave function indicated that the mixing between L-2 and L-3 edges was significantly large in Cr3+ L-2,L-3-edge XANES spectra for both ruby and alpha-Cr2O3. In addition, XANES spectra showed that the L-3-edge component significantly mixed in the L-2-edge peaks, while the L-3-edge component also significantly contributed to the intensity of L-2-edge. The theoretical MCD spectra for ruby also well reproduced the experimental one. We also investigated the validity of the sum rules quantitatively by comparing the magnetic moments calculated from the theoretical spectra using the sum rules and those calculated directly from the explicit many-electron wave functions. The orbital moments by both methods were almost zero, and the spin moments had 10% difference between these methods. The results of the configuration analysis indicated that the magnitude of the mixing between L-2 and L-3 edges could be the major cause of this discrepancy. (C) 2011 American Institute of Physics. [doi:10.1063/1.3672442]