Magnetic studies on the superconducting oxide ErBa 2Cu 3O 7−y

Abstract

Magnetic studies have been carried out on the oxide superconductor ErBa 2Cu 3O 7−y ( T c =88 K) at various temperatures and fields. From the hysteresis loop recorded at 4.2K, the values of the lower critical field and magnetization critical current densities are determined. In the superconducting state, the magnetization is found to become positive at some temperature depending on the applied field. This is thought to be due to some field penetration under the influence of which the paramagnetism of Er ions overtakes the diamagnetic response. From the susceptibility data above the superconducting state, the effective rare earth ion moment is found to be very close to its free ion value. In spite of the large moment, the rare earth ion has no discernible effect on T c.