Electronic structure of RuSr2EuCu2O8 studied by x-ray absorption and photoemission spectroscopies

Local electronic structures of ruthenocuprate RuSr₂EuCu₂O₈ (RuEu-1212) were investigated by using x-ray absorption near-edge structure (XANES) and valence-band photoemission (VB-PES) measurements at room temperature, 80 K, and 25 K. The XANES results indicate that when RuEu-1212 is below Curie temperature, T_M, electrons are transferred not only from Cu 3d states, but also from Ru 4d states, to O 2p orbitals. Additionally, the partial spectral weight distributions derived from VB-PES measurements provide evidence of a weak overlapping between Ru 4d states and strongly Cu 3d-O 2p hybridized states below the Fermi level, which results in a weak coupling between the CuO₂ and RuO₂ layers. The analysis of extended x-ray absorption fine structure shows that the appearance of weak ferromagnetism and superconductivity is accompanied by a significant decrease of dynamic local lattice distortions of high-shell Cu-Sr and Ru-Sr bonding in RuEu-1212.