Correlation between magnetic hysteresis and magnetic relaxation in YBaCuO single crystals

The dependence of the magnetic momentm obtained from the hysteresis loops on the speed of the magnetic field sweep\(\dot H\) =dHext/dt is explained on the basis of Anderson's interpretation of the magnetic flux creep. In addition, a phenomenological model is suggested which predicts a linear dependence ofm on ln ‖\(\dot H\)‖ with the slope ∂m/∂ ln ‖\(\dot H\)‖, numerically equal to the relaxation rate ∂m/∂ ln(t) from the usual magnetic relaxation. Such linear relations betweenm and ln ‖\(\dot H\)‖ were observed experimentally in single crystals of YBaCuO. Preliminary experiments on the complementary time dependent relaxation ofm after a simulated step change ofHext gave mostly relaxation rates close to the predicted values. The model here presented also enables one to compare the critical state in the superconductor at a field sweep rate\(\dot H\) with the critical state at some timeteff after a step change ofHext. The values of\(\dot H\) analyzed in our experiments actually correspond to the critical state at timesteff between0.04 and4 sec after an imaginary large step change ofHext.