Correlation between magnetic hysteresis and magnetic relaxation in YBaCuO single crystals

TLDR: In this paper, a phenomenological model is suggested which predicts a linear dependence of the magnetic momentm obtained from the hysteresis loops on the speed of magnetic field sweep, numerically equal to the relaxation rate ∂m/∂ ln(t) from the usual magnetic relaxation.

Abstract: The dependence of the magnetic momentm obtained from the hysteresis loops on the speed of the magnetic field sweep $$\dot H$$ =dH ext/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 ofH ext 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 timet eff after a step change ofH ext. The values of $$\dot H$$ analyzed in our experiments actually correspond to the critical state at timest eff between0.04 and4 sec after an imaginary large step change ofH ext.