AC susceptibilities of grain-textured superconductors

In-phase χn′ and out-phase χn″ components of nth harmonics of AC susceptibility with measuring parameters of a DC magnetic field Bdc, an amplitude Ba and a frequency f of the superimposed AC magnetic fields give substantial information of the superconducting properties. In low-Tc metallic superconductors, χ1′ shows smooth transition and χ1″ does single peak. High-Tc oxide superconductors with anisotropic and grain-textured structures show deformed complex characteristics. Double peaks in χ1″ and shoulders in χ1′ appear in AC susceptibility of Hg-1223 superconductors.Instead of simple Bean model, a grained model, where the superconducting grains are immersed in weak superconducting matrix, are proposed. The susceptibilities numerically analyzed using the model show varied and deformed curves and are successfully compared with the measured results.