Development of the method for low-temperature investigations of HTSC systems on an X-ray electron magnetic spectrometer
Peculiarities of the chemical structure of bulk polycrystalline samples of the high-temperature superconductors Bi2Sr2CaCu2O8, BiSrCaCu2O5.5, BiSrCaCu3O8, and YBa2Cu3O7 − δ have been investigated in detail at room and superconducting temperatures on an X-ray electron magnetic spectrometer equipped with an attachment for low-temperature studies. It is shown that covalent bonding is formed at a superconducting temperature between copper and oxygen due to Cu2+ ions. Due to the enhancement of the d(Cu)–p(O) hybridization of copper and oxygen electrons in the superconducting state, the d-electron density increases near E F. The occurrence of additional peaks in the O1s and Sr3d (Ba3d) spectra after transition of the system to the superconducting state indicates changes in the nearest environment of O and Sr (Ba) atoms, in particular, the transition of Sr atoms to a higher oxidation state.
KeywordsSuperconducting State High Oxidation State HTSC Sample HTSC Compound HTSC System
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