AC Hysteresis Losses near the Glass-liquid Transition Temperature in High-Tc Cuprate Superconductors

The AC loss in high-Tc superconductors near the glass-liquid transition temperature, Tg, is studied numerically and theoretically. It is shown that the AC loss in a slab sample under a DC bias magnetic field depends noticeably on the angular frequency, ω, and hence, cannot be described by the usual critical state model using critical current density, Jc, defined with the aid of the electric field criterion. However, the AC loss including the flux flow loss is shown to be describable quantitatively by present handy theoretical expression, which has the same form as the well-known expression based on Bean's critical state model except that Jc is replaced by the effective critical current density, Jce(ω).