Intensity of the EPR spectrum in quenched samples of Yba2Cu3Ox compounds

The temperature dependence of the intensity of the EPR signal is measured in the high-temperature superconductor YBa2Cu3O6.85 and in the nonsuperconducting compound YBa2Cu3O6.25. The copper-oxygen cluster model with spin S=2 best describes the results obtained in a sample with an oxygen index of 6.25. The interpretation of the experimental results for a sample with an oxygen index of 6.85, on the other hand, requires the additional assumption that the cluster S=2 also has a 200-fold degenerate level at a distance ∼110 K.