AC Susceptibility Studies of Anisotropy in Sm-123 Superconductors

The main cause of the degradation in the oxide superconductors is considered to originate in the inter-granular link region among the superconducting grains. For analytical study of the granular structure, the grained Bean model is proposed, where the superconducting grains are immersed in the interconnecting link superconductors. Difference of the superconducting characteristics of the grain and the link, pinning penetration depths B_pg, B_pl and grain volume factor f_g, introduces a variety of deformation on the AC susceptibility curves, such as double peaks in the imaginary part χ^´´ and plateaus in the real part χ^´. From the dependence of χ^´ and χ^´´ of AC susceptibility on temperatures T and DC magnetic fields B_dc in grain-aligned Sm-123 superconductors, critical current densities, grain sizes and their anisotropic nature can be estimated and discussed comparing with the existing data.