Flux Creep, Pinning Potential and Critical Current Density in Bi2Sr2Ca1Cu2Ox Single Crystals

Flux creep characteristic at 4.4 K in Bi₂Sr₂Ca₁Cu₂O_x single crystals grown by flux method has been measured as a function of magnetic field applied parallel to the c-axis. The logarithmic relaxation rate of the magnetization dM/d ln t is analyzed on the basis of the flux creep model in combination with an extended Bean’s critical state model in which n-th power dependence (0≤q n≤q 1) of critical current density on magnetic field is assumed. The pinning potential and the zero-temperature critical current density are estimated to be 0.014∼ 0.056 eV and 10⁴∼ 10⁵ A/cm², respectively, depending on oxygen partial pressure of the crystal growth environment.