YBCOセラミック超伝導体の粒間磁束デピニングの研究

抄録

We have studied intergranular flux depinning in Y₁Ba₂Cu₃O_7-δ ceramics. We measured do magnetization as a function of temperature at different applied magnetic fields for field-cooled ceramic and pressed-powder samples. Fast cooling of the ceramic sample down to low temperatures causes more intergrain flux trapping than slow cooling. During warming the flux depins which is associated with an increased Meissner expulsion. Two characteristic temperatures indicating the onset and completion of depinning allowed to develop a (H, T) magnetic phase diagram for the intergrain flux depinning, that occurs for magnetic fields and temperatures over a range 0-1500G and 92-30K, respectively.