SEPARATE PARAMAGNETISM AND SUPERCONDUCTIVITY IN YBA2CU3OZ

The magnetic properties of YBa2Cu3Oz with different values of z in the temperature range 1.5–300 K were measured and compared with those of DyBa2Cu3Oz and EuBa2Cu3Oz. The susceptibility data of YBa2Cu3Oz and DyBa2Cu3Oz followed the Curie–Weiss law above Tc, while those of EuBa2Cu3Oz exhibited the Van Vleck and Frank behavior [Phys. Rev. 34, 1494 (1929)] with σ=33. The paramagnetism persisted even below Tc. The effective moment per copper ion increased as the oxygen content decreased. The results suggest that the paramagnetism in YBa2Cu3Oz originates mainly from the nonsuperconducting domains of the material which have disordered oxygen vacancies or have lower oxygen content than the superconducting ones.