Resonant X-ray scattering in the presence of several anisotropic factors

The general form of the X-ray susceptibility tensor near absorption edges is found when several anisotropic factors, such as the anisotropy of local atomic environment, magnetic ordering and orbital ordering, simultaneously exist in a crystal. Different phenomenological approaches are used to obtain the explicit form of the susceptibility tensor and to find the contributions from each anisotropic factor separately as well as `combined' terms owing to their simultaneous existence. The results of the theoretical treatment are applied to the resonant diffraction by La_0.5Sr_1.5MnO₄ below the Néel temperature, where charge and orbital ordering coexist with anisotropy of local atomic environment and magnetic ordering.