It was recalled that important superconducting characteristics could be deduced from the shape of magnetization curves. The critical current densities, irreversibility fields and losses of the superconductors could be estimated from hysteretic curves. The magnetic field and temperature dependences of the pinning strength Fp in type-II superconductors was known to be well-described by the scaling law of the pinning force, Fp = AHC2m(B/BC2)γ(1-B/BC2)δ, where HC2 was the upper critical field and γ, δ and m were the pinning parameters. In high-temperature superconductors, the scaling law failed to describe the pinning properties since the irreversibility field Birr was much smaller than the upper critical field, BC2. Conversion of the field dependence term in the scaling law was accomplished by replacing BC2 by Birr. The magnetization curves, computed differentially by using the scaled JC with the pinning parameters of γ, δ and m, exhibited various shapes and could be fitted well to the observed curves of MgB2 superconductors over wide ranges of temperatures and magnetic field.

Magnetization Curves and the Scaled JC Characteristics in Various Superconductors. N.Sakamoto, T.Akune, Y.Matsumoto, H.R.Khan, K.Lüders: Physica C, 2005, 426-431[1], 726-30