Reduced flux motion via flux creep annealing in high- J_c single-crystal Y₁Ba₂Cu₃O₇

We investigated the stabilization of magnetic flux in a high-temperature superconductor (a proton-irradiated Y1Ba2Cu 3O7 crystal), by operating with subcritical current density J. Using the thermal history to obtain an induced current density J≤Jc, we observed a drastically reduced relaxation rate dM/dt (M=magnetization), after "flux creep annealing". The results show that the field gradient ∼J∼M determined the relaxation rate, independent of the sample's H-T history, in agreement with recent theory.