Unusual behavior of thermoremanent magnetization in single crystal Bi2212

Examining a Bi2212 superconductor for useful applications, the rapid decline of critical current (I_c) with an increase in temperature prevents the high-temperature operation for a superconducting magnet when using a Bi2212 cable. In this study, we found a phenomenon that indicates the rapid decline of I_c when using a Bi2212 single crystal. Thermoremanent magnetization shows an anomalous dispersive behavior in AC susceptibility when kept below 20 K. The analysis of decay in DC magnetization, based on weak collective pinning and vortex glass theory within the single-vortex pinning regime, describes a drastic change in the activation energy of vortex pinning. To explain these peculiar characteristics, a model that originates in variable range hopping while in the metastable state is suggested.