Spettroscopic features of the Cu++ centers in YBa2Cu3O7-x by electron paramagnetic resonance

Electron paramagnetics resonance line shapes of the Cu++ centers in the high-Tc superconductor YBa2Cu3O7-x pellets are analytically reproduced by a computer simulation. The comparison between theoretical and experimental spectra is quite good for all investigated temperatures provided a partial orientation of paramagnetic complexes within a randomly oriented matrix is considered. Angle-resolved electron paramagnetic resonance measurements on pellets confirm this peculiarity of ceramic superconductors. Spectroscopic factors of the two non equivalent Cu++ environments as deduced by the computer analysis, are repoted and discussed versus temperature