Reduction of Flux Creep after High-Temperature Magnetization

Abstract

After a long period of creep process, the slope of the magnetic flux distribution becomes less steep and the flux distribution seems to be effectively equal to that magnetized at a higher temperature. Then the gentle creep is expected, if the flux distribution at an operating temperature T o is replaced with that at higher temperature T o+ΔT by cooling a YBaCuO superconductor magnetized at higher temperatures (HTM). By this HTM, drastic reductions in the creep rate by one order of magnitude were observed for a temperature increment ΔT ≥ 3K at T o ranging from 40 to 77K in melt-growth YBaCuO superconductors. Time scale shift t off falls the HTM creep data on the normal creep line. An expression for ΔT s is given, where a linear decay rate of critical current (1/J)(dJ/dt) at ΔT > ΔT s becomes small than an allowable linear rate S(sec-1) which is necessary for a superconducting device performance.