Specific Heat of YBa2Cu3O7-δ, 0≤δ≤0.2:: Concentrations of paramagnetic centers and values of other parameters as functions of δ

The concentrations of paramagnetic centers and the values of other parameters, including the Debye temperature and the coefficient of the zero-field, temperature-proportional term, are reported as functions of delta. The concentration of paramagnetic centers does increase with increasing delta but, in striking contrast with the widely held expectation that the increase would be comparable to the increase in the concentration of O vacancies, it is as much as 2 orders of magnitude smaller. A new expression for the specific heat that takes into account the presence of spin-2 as well as spin-1/2 paramagnetic centers gives an accurate representation of the experimental data.[S0031-9007(99)08491-4].