Theory of orbital orderings and excitations in perovskite manganites - Their observation by resonant X-ray scattering

The orbital orderings and excitations in perovskite manganites and experime ntal methods for their observation by resonant x-ray scattering are theoret ically investigated. In the elastic scattering for the ordering, an origin of the orbital dependence of the atomic scattering factor is identified and a method to distinguish several types of the orbital ordering is considere d. As a probe to detect the orbital excitation, a possible mechanism by the resonant inelastic x-ray scattering is proposed.