Resonant X-Ray Scattering from CeB₆

Abstract

We calculate the resonant x-ray scattering (RXS) spectra near the Ce L_III absorption edge in CeB₆, on the basis of a microscopic model that the 4ƒ states of Ce are atomic while the 5d states form an energy band with a reasonable density of states. In the initial state, we employ an effective Hamiltonian of Shiina et al. [J. Phys. Soc. Jpn. 66 (1997) 1741] in the antiferro-quadrupole (AFQ) ordering phase, while we construct the wave function consistent with the neutron scattering experiment in the magnetic ground state. In the intermediate state, we take full account of the intra-atomic Coulomb interaction. Without assuming any lattice distortion, we obtain sufficient RXS intensities on the AFQ superlattice spot. We obtain the spectral shape, the temperature and magnetic field dependences in good agreement with the experiment, thus demonstrating the mechanism that the intensity is brought about by the modulation of 5d states through the anisotropic term of the 5d-4ƒ Coulomb interaction. In the magnetic ground state, a small pre-edge peak is found by the E₂ process. On the magnetic superlattice spot, we get a finite but considerably small intensity. The magnetic form factor is briefly discussed.