A theory of the absorption and the resonance-enhanced diffraction of soft x-rays by anisotropic ferrous magnetic moments in FeNb2O6

Some of the interesting magnetic properties of ferrous niobate have recently been attributed to the orbital angular momentum of the iron atom. In the present work, the spin and orbital components of the magnetic moment are shown to make distinctive appearances in the resonant contribution to the scattering length for the electrostatic scattering of x-rays, from which the dichroic signals in the attenuation coefficient and the Bragg diffraction cross-section are derived. Quantitative predictions are made for the circular and linear dichroic signals of ferrous atoms in FeNb2O6, and these are compared to the corresponding signals predicted for free ferrous atoms. In all cases, the analytic expressions for the dichroic signal possess a relatively simple structure.