Local moments, diamagnetism, and time-dependent magnetic response of high-temperature superconductors

Abstract
The magnetic properties of high-Tc superconductors RBa2 Cu3O7−δ with R=Y, Gd were investigated in the temperature range 4.2–300 K. To first order, no interaction was found between superconductivity and paramagnetism in the zero-field-cooled state of the Gd-doped samples: after correction for the Curie–Weiss magnetization, the diamagnetism of these samples is very close to that of the Y-doped samples. This suggests that the superconducting screening of an applied field has little effect on the field seen by the R species. The diamagnetic screening is found to be strongly time dependent due to flux penetration, whereas the magnetic ions see the applied field without delay.