The effect of core-valence intra-atomic quadrupolar interaction in resonant x-ray scattering at the Dy M4,5 edges in DyB2C2.

The dependences on energy of the resonant soft x-ray Bragg diffraction intensities in DyB(2)C(2) for the (00½) reflection at the Dy M(4,5) edges have been calculated with an atomic multiplet Hamiltonian including the effect of the crystal field and introducing an intra-atomic quadrupolar interaction between the 3d core and 4f valence shell. These calculations are compared with experimental results (Mulders et al 2006 J. Phys.: Condens. Matter 18 11195) for the antiferroquadrupolar and antiferromagnetic phases of DyB(2)C(2). We reproduce all the features appearing in the (00½) reflection energy profile in the antiferroquadrupolar ordered phase, and we reproduce the behaviour of the resonant x-ray scattering intensity at different energies in the vicinity of the Dy M(5) edge when the temperature is lowered within the antiferromagnetic phase. These calculations show that a detailed description of the energy dependences of resonant x-ray scattering signals at the M edges in 4f and 5f systems with multipolar ordering may require the inclusion of an aspherical intra-atomic Coulomb interaction.