Lattice distortion and resonant X-ray scattering in DyBC

Igarashi, Junichi; Nagao, Tatsuya*

We study the resonant X-ray scattering (RXS) spectra at the Dy L_ absorption edge in the quadrupolar ordering phase of DyBC. Analyzing the buckling of sheets of B and C atoms, we construct an effective model that the crystal field is acting on the 5d and 4f states with the principal axes different for different sublattices. Treating the 5d states as a band and the 4f states as localized states, we calculate the spectra within the dipole transition. We take account of processes that (1) the lattice distorion directly modulates the 5d states and (2) the charge anisotropy of the quadrupole ordering 4f states modulates the 5d states through the 5d-4f Coulomb interaction. The former process is found to give dominant contribution to the spectra.