Magnetic circular dichroism in x-ray resonant Raman scattering in perpendicular geometry fromCoFe2O4and Co metal: A comparison of valence and inner-shell channels

Abstract

We present results on resonant Raman scattering (RRS) in perpendicular geometry excited with circularly polarized x rays at the Co ${L}_{3,2}$ edges in ${\mathrm{CoFe}}_{2}{\mathrm{O}}_{4}$ (Co ferrite) and Co metal. In this geometry the incident x-ray beam is perpendicular to the magnetization and the magnetic dichroism is only present in the RRS and not in the absorption. We compare the $3s\ensuremath{-}\mathrm{R}\mathrm{R}\mathrm{S}$ channel terminating in an inner shell $3s$ hole and extra $3d$ electron ${(2p}^{6}{3d}^{n}\ensuremath{\rightarrow}{2p}^{5}{3d}^{n+1}\ensuremath{\rightarrow}{2p}^{6}{3s}^{1}{3d}^{n+1})$ and the $3d\ensuremath{-}\mathrm{R}\mathrm{R}\mathrm{S}$ channel ending in a $3d$ electron-hole pair ${(2p}^{6}{3d}^{n}\ensuremath{\rightarrow}{2p}^{5}{3d}^{n+1}\ensuremath{\rightarrow}{2p}^{6}{3d}^{n}).$ The work is based on the measurement of the spectra vs the incident photon energy and integrated over the scattered photon energy. In both samples the dichroism of the inner-shell channel is about an order of magnitude larger than that of the valence channel. The result is explained by a theory based on the fast-collision approximation. We show that this theory provides a general way to choose the optimum scattering channel in the study of magnetic dichroism in perpendicular geometry. The impact of the results is briefly discussed.