多結晶YBa_2Cu_3O_<7-δ>超伝導体の局所臨界電流密度の磁場依存性I-測定法 Magnetic Field Dependence of Local Critical Current Density of Polycrystalline YBa_2Cu_3O_<7-δ>I-Method of Measurement
We have proposed the new method for measuring transport critical current density J<SUB>ct</SUB> of high-T<SUB>c</SUB> polycrystalline superconductors on the basis of the exponential critical-state model J<SUB>ct</SUB>=J<SUB>0</SUB> exp(- B<SUB>inter</SUB>/B<SUB>0</SUB>), where J<SUB>0</SUB> and B<SUB>0</SUB> are constant, andB<SUB>inter</SUB> is intergrain magnetic-flux density. Full-penetration field H<SUB>p</SUB> and remnant-magnetization saturating field H<SUB>6</SUB> are measured directly from the magnetization hysteresis and the remnant-magnetization curve of the sample, respectively. The model parameters J<SUB>0</SUB> and B<SUB>0</SUB> are derived by substituting H<SUB>p</SUB> and H<SUB>s</SUB> into critical-state equations. A critical current density measured by four-probe method is averaged one of local J<SUB>ct</SUB> over the sample exposed to self magnetic field generated by applied current, and increases with decreasing the cross-sectional area of the sample, while the intrinsic property of local J<SUB>ct</SUB> can be estimated by the method proposed in this work.
粉体および粉末冶金 44(2), 162-167, 1997-02-15
Japan Society of Powder and Powder Metallurgy