Band Structure and Crystal-Field Excitations of La1-xLuxVO3 Crystals Studied by Soft X-ray Spectroscopies

Speaker: Bo Chen

When: November 20, 2013 (Wed), 03:00PM to 04:00PM (add to my calendar)
Location: PRB 261

This event is part of the Departmental Seminars.

Dissertation Committee: Kevin Smith, Richard Averitt, Karl Ludwig, Anders Sandvik, and Scott Whitaker

Abstract:

The rare-earth orthovanadates, RVO3, offer a fascinating phase diagram with both orbital- and spin-ordering phenomena, owing to their two-fold electron occupations of the triply degenerate V t2g orbitals. Their spin-orbital phase diagram was found to evolve with temperature, R-site ionic size, and R-site substitution, and exhibit switching between different patterns of spin and orbital order. In order to understand these effects of the rare-earth ionic size and the orbital ordering, we report a soft x-ray spectroscopic study of the electronic structure of Lu1-xLaxVO3 single-crystals, which approach both the smallest and largest rare-earth ionic radii. The x-ray absorption (XAS) and emission (XES) spectra at the O K-edge, which probe both the unoccupied and occupied O 2p partial density of states, closely measure the O 2p-V 3d hybridization and reveal the strong dependence of the O 2p-R 5d hybridization with temperature and R-site cation. Good agreement is obtained between the experimental spectra at the O K-edge and the theoretical O 2p PDOS calculated within the local spin density approximation [L(S)DA], including the static Coulomb repulsion parameter, U, self-consistently (LSDA+U). Moreover, the resonant inelastic x-ray scattering spectra (RIXS) at the V L3-edge, which probe the intra-site dd* transitions, directly measure the 3d orbital splitting of single vanadium-site as a function of temperature and R-site ionic size. Together, these combined spectroscopic techniques provide a detailed study of the band structure and the crystal-field excitations of Lu1-xLaxVO3 with varied R-site ionic radius during phase transitions.