Electronic Structure Of Sr2ruo4: X-Ray Fluorescence Emission Study

The results of measurements of O 1s total x-ray-fluorescence yield and Ru N-2,N-3 and O K-alpha x-ray fluorescence emission spectra of Sr2RuO4 and Sr2Ru4.25 are presented. An excitation energy dependence of the O K-alpha x-ray emission spectra (XES) was observed in both compounds. The energy dependence of the spectra is attributed to the excitation of inequivalent O(1) in-plant and O(2) apical oxygens. The O(1) 2p and O(2) 2p density of states distribution in the valence band of Sr2RuO4 was found to be different in accordance with the results of band-structure calculations. O(1) 2p states are found to be mixed with Ru 4d(t(2g) states providing the formation of pi bonds. While the O K-alpha XES spectra are in fair agreement with hand structure calculations, the theoretical two-peak distribution of Ru N-2,N-3 XES is found to be different with respect to the intensity ratios and widths of the peaks of Ru N-2,N-3 XES. These differences an attributed to a decrease of intensity of radiative 4d --> 4p transitions in the vicinity of the Fermi level (where the localization of Ru 4d states is higher than at the bottom of the valence band) due to a strong Kuster-Kronig transition.