FLUX CREEP IN FLUORINE-DOPING Bi(Pb)-Sr-Ca-Cu-O BULK SUPERCONDUCTOR

We report the field and time dependences of zero field cooled magnetization for fluorine-doped Bi1.7Pb0.3Sr2Ca2Cu3Oy bulk superconductor. By fluorine-doping, the field dependences of both flux creep and pinning potential exhibit some new behaviours suggesting S = dM/d ln t ∝ H1/2 for the field range from H p to 1000 Oe, U0(H)∝ exp (−H/30) for the field below H p and U0(H)∝H−α with α=3/2 for the field above H p .