Resonant X-ray Scattering from URu₂Si₂

Abstract

Based on a localized crystal electric field model for the U⁴⁺ in the (5f)²-configuration, we analyze the resonant x-ray scattering spectra around U M_IV and M_V edges in URu₂Si₂, taking full Coulomb and spin–orbit interactions into account. We consider two level schemes, a singlet model of Santini and Amoretti and a doublet model of Ohkawa and Shimizu [J. Phys.: Condens. Matter 11 (1999) L519], and assume the antiferroquadrupolar (AFQ) order and the antiferrooctupolar (AFO) order as candidates for the ambient pressure phase as well as the antiferromagnetic (AFM) order as that for the high pressure phase. It is found that the spectral shapes as a function of photon energy are independent of the assumed level scheme, but are quite different between the AFQ and AFM phases, while the AFO phase shows no scattering intensity. This may be useful to determine the character of the ordered phase.