On The Scaling Analyses Of The Flux Pinning Force Density Estimated For Two Types Of Mgb2 Specimens

Magnetic hysteresis loops have been measured for polycrystalline and powder MgB2 samples. Hysteresis loop width Delta M measured for polycrystalline sample was less than one order of magnitude smaller than that measured for powder sample. Magnetic field dependence of the critical current density estimated from the Delta M is essentially divided into three regions. The irreversibility field B-irr for each sample has been derived from so called Kramer plots using relevant magnetic field dependence. The scaling law of the reduced pinning force density was satisfactorily applied to the experimental results for each sample by using thus determined B-irr. If we define the B-irr as a field at which the critical current density becomes 10(6)(A/m(2)), such scaling law is apparently applicable to polycrystalline sample and not applicable to powder sample. Such discrepancy may come from that the B-irr by two types of definition belongs to different flux regime.