Critical magnetic field and critical temperature of the superconductivity in the yttrium oxides

The origin of the high temperature superconductivity (HTS) of the metallic oxides is discussed. In the framework of the two-zone model it is shown that the critical temperature of the HTS depends on the densities-of-state (DOS) of the holes at the Fermi level both in the two-dimensional band in the layers and in the one-dimensional bands in the chains. The upper critical magnetic field is determined both in the mean field theory temperature region and in the region of strongly interacting fluctuations. It is shown that the ordering of the oxygen defects leads to the increase of the critical temperature.