Relationships between X-ray photoelectron spectra, structure and superconductivity in LnBa2Cu3O7-x
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X-ray photoelectron spectroscopy has been carried out on HoBa2Cu3O7-x (on abraded, fractured and ion beam reduced surfaces). These measurements show that there are only minor differences with similarly obtained results from YBa2Cu3O7-x. The spectral features of the Ln species (Y and Ho), the O 1s, and Ba 3d envelopes are considered in some detail. The low energy contribution to the O 1s envelope has been assigned in part to the effects of Ba-O bonding, either in the LnBa2Cu3O7-x material, or in BaO in minor phase regions, and in part to the effects of the electronic linkage of the Cu planes in the superconducting compound. The anomalous low binding energy contributions to the Ba 3d envelope are also specific to the electronic structure of these materials. It is likely that Ba (and Sr and Ca for the Bi-Sr-Ca-C-O system) plays an important electronic, as well as structural role, in promoting high temperature superconductivity.
Zeitschrift fur Physik B : Condensed Matter