Simulation of the spectroscopic and magnetic properties of RE(III) ions in RE oxychlorides based on exact crystal structure from Rietveld refinements

The procedures to calculate the 4f(N) energy level schemes - together with the related properties such as the paramagnetic susceptibility - of the trivalent rare earth ions (RE3+) in the tetragonal RE oxychlorides (REOCl, RE=La-Nd, Sm-Ho and Y) from structural data are presented. The methods include the determination of coherent and reliable structural parameters from X-ray powder diffraction measurements using Rietveld analyses. The measurement of the absorption and luminescence spectra of the RE3+ ions from the IR to UV region yield the experimental 4f(N) energy level schemes which are then simulated with a phenomenological model involving the parametrization of the inter- and intra-ionic interactions. Parallel calculations - already proven to be successful for ionic systems such as RE oxyfluorides - are based on the modified point charge model (PCEM). The more covalent simple overlap (SOM) model is also applied and compared to the other results. Finally, the paramagnetic susceptibility of the pure oxychlorides as a function of temperature was calculated using the eigenfunctions and eigenvalues from the phenomenological simulation of the experimental 4f(N) energy level schemes. (C) 2000 Elsevier Science S.A. All rights reserved.