Resonant x-ray scattering from multi-k magnetic structures

Resonant x-ray magnetic scattering gives access to magnetic Bragg reflections, which are forbidden in neutron and nonresonant x-ray diffraction. The symmetry constraints on the magnetic configuration implied by processes involving a rotation of the photon polarization, where the scattering operator projects the local magnetization onto two orthogonal axes, as opposed to the single-axis projection of conventional techniques, bring important new light to bear in the determination of magnetic structures. As an example, we have established the multi-k nature of the intrinsic magnetic configuration in UAs0.8Se0.2 through the presence of peaks in the scattering pattern of the form (k(i)+k(j)) with inot equalj. Their identification, by a distinct energy, momentum, polarization, and azimuthal dependence, yields unique information on the unperturbed magnetic structure. In the present case, working at the M-4 uranium edge, the peaks have similar to1% of the intensity of the main resonant (0 0 k(i)) magnetic satellites. The technique, free of the ambiguities introduced by application of external perturbations which hamper interpretation of such multi-k structures by conventional diffraction, may find application in rare-earth and transition-metal compounds despite the weaker enhancements of the respective L and K resonances.