Effect of reductive treatment on the magnetic properties of HoBa2Cu3Oy andNdBa2Cu3Oy oxide systems

The effect of the reductive treatment of perovskite-like RBa2Cu3Oy (R = Ho, Nd) complex oxides in a CO atmosphere on their superconducting and magneti c properties is studied by ESR spectroscopy. ESR spectra of initial RBa2Cu3 Oy phases exhibit only a low-field absorption signal in the zero field (T = 77 K). This signal disappears after the exposure of test samples to carbon monoxide. The analysis of ESR spectra of reduced samples points to the for mation of regions with high local concentrations of isolated Cu2+ ions and Cu2+-Cu2+ dimers. The concentration of these paramagnetic species significa ntly decreases with an increase in the degree of reduction.