Study on Effects of Pr to Site Specific Electronic Structure of High Tc Superconducting Oxide probed by soft-x-ray absorption and emission spectroscopy

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The site specific electronic structures of oxygen in PrBa_2Cu_3O_7 and YBa_2Cu_3O_7 compounds were recorded from the measurements of O 1 s total x-ray-fluorescence yield and O Kα x-ray fluorescence emission spectra of PrBa_2Cu_3O_7 and YBa_2Cu_3O_7 single crystals. The polarization dependence of the x-ray absorption spectra(XAS) near oxygen absorption edge in the specimens is attributed to the excitation of four in equivalent oxygen sites : O(1) chain, O (2) and O(3) in-plane, and O(4) apical oxygens and the hole states of the oxygens were specified. Thereafter, we obtained the site specific electronic structure by the O Ka x-ray emission spectra (XES), exciting the target oxygen by the use of polarization and energy dependence of hole state. The evidence of hybridization between the Pr 4f and O p-π orbital was observed in the spectrum of O(2,3) in plane of PrBa_2Cu_3O_7) which was predicted by Fehrenbacher : and Rice. The spectrum is consistent with the band theoretical calculation by Liechtenstein and Mazin, based on the Fehrenbacher and Rice model.The site specific electronic structures of oxygen in PrBa_2Cu_4O_8 and YBa_2Cu_4O_8 compounds were recorded from the measurements of O 1 s total x-ray-fluorescence yield and O Ka x-ray fluorescence emission spectra of the single crystals. Consistent results with the theory by Fehrenbacher and Rice were obtained also in these compounds