Influence of DC Field Sweep Rate on Non-Resonant Microwave Absorption in a YBa2Cu3Ox Superconductor

Non-resonant microwave absorption intensity and reverse-sweep hysteresis were measured as a function of dc field sweep rate at 77 K in a YBa2Cu3Ox bulk sample. Intensity of the non-resonant microwave absorption increases with increasing the sweep rate and saturates at higher sweep rates. The sweep rate influence is stronger at lower fields than at higher fields. We interprete the sweep rate dependence of the non-resonant microwave absorption in terms of much different flux profiles for slower (equilibrium) and faster (transient) sweep rates. Sweep rate dependence of the hysteresis qualitatively follows the dynamical model calculation of Portis, which takes into account the Anderson type of time decay of currents at sample surface.