Resonant X-ray scattering in transition metal and rare-earth materials

X-Ray resonant methods reveal the occurrence of symmetry breaking effects: lattice distortion, onset of magnetic order and orbital occupancy order and asphericity of the electronic shells. All these effects reflect electronic properties. Three main properties of X-ray resonance are presented: the large enhancement of scattering amplitude, the chemical selectivity and the sensitivity to the symmetry of electronic levels. Applications in the observation of charge, spin and orbital ordering illustrate the strength of the X-ray resonant methods. (C) 2001 Elsevier Science B.V. All rights reserved.