DEPENDENCE OF THE LOW-TEMPERATURE SPECIFIC-HEAT OF YBA2CU3O7-DELTA ONDELTA AND MAGNETIC-FIELD - CONCENTRATIONS OF SPIN-2 AND SPIN-1 2 PARAMAGNETIC CENTERS/

Specific heat data on two samples of YBa2Cu3O7-delta with relatively l ow concentrations of paramagnetic centers show the presence of both sp in-2 and spin-1/2 moments. Measurements on one sample following increm ental increases in delta show that for delta less than or equal to 0.2 approximately one spin-1/2 moment is produced for each 100 O vacancie s, with no substantial increase in the linear term of the specific hea t. For several reasons it is concluded that these O-vacancy related mo ments are different from those that have figured in previously reporte d correlations with parameters characteristic of the superconductivity .