Electron paramagnetic resonance or the normal and superconducting phases of the system Y-Ba-Cu-O

The properties of the copper ion in the normal and superconducting phases of a Y-Ba-Cu-O ceramic, which are characterized by different degrees of oxygen deficit, are investigated experimentally using the electron paramagnetic resonance method. It is shown that both normal and superconducting phases can be identified by the presence of a single or double EPR line. The quality of the superconducting ceramic can also be estimated from the line intensity ratio.