Trapped low magnetic field dynamics in YBCO single crystals

Trapped low magnetic flux dynamics including local ones are investigated in YBCO single crystals in the strong thermal fluctuations domain near the superconducting phase transition temperatures. The essential difference from quasi-logarithmic isothermal relaxation of a magnetization behavior (observed earlier in high magnetic fields) was established. Within the framework of classic model of a thermal activated vortices creep the estimation of an effective pinning potential was made at these temperatures.