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Publisher: American Physical Society
Languages: English
Types: Article
Subjects: 11000/12
We present a detailed description of a first-principles formalism for magnetic scattering of circularly polar- ized x rays from solids in the framework of the fully relativistic spin-polarized multiple-scattering theory. The scattering amplitudes are calculated using a standard time-dependent perturbation theory to second order in the electron-photon interaction vertex. Particular attention is paid to understanding the relative importance of the positive- and negative-energy solutions of the Dirac equation to the scattering amplitude. The advantage of the present theory as compared with other recent works on magnetic x-ray scattering is that, being fully relativistic, spin-orbit coupling and spin-polarization effects are treated on an equal footing. Second, the electron Green’s function expressed in terms of the path operators in the multiple-scattering theory allows us to include the contribution of the crystalline environment to the scattering amplitude. To illustrate the use of the method we have done calculations on the anomalous magnetic scattering at the K , L_II , and L_III absorption edges of ferromagnetic iron.
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    • 36 If an atomic LII,III-subshell core-hole lifetime value of G50.24 eV is used, then the dichroism curve ~with or without an extra Gaussian instrumental broadening convolution on the cross section! contains quite profound oscillations, which are not present in the measured dichroism curves provided by Kao et al. ~Ref. 7!. Furthermore, using G51 eV reproduces well all the features observed in the measured dichroism curve by Kao et al. ~Ref. 7!. We have also noticed that using G values larger than about 1 eV will not change the qualitative nature of the dichroism curve. We want to stress that G is just a parameter reflecting the manybody effects involved in the x-ray-scattering process, and is not linked in any systematic manner to the ab initio part of the theory, i.e., to the LDA electronic structure.
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