Study of microstructure and magnetic properties in copper oxide superconducting systems through AC magnetic susceptibility
Two samples of high temperature superconductors with the general compositions YBa2Cu3O and GdBa2Cu3O were prepared by solid state reaction. The X-ray diffraction patterns and the Scherrer's equation were used to obtain the lattice parameters and the average grain size, D. We explored the microstructure of both samples using the temperature dependence of AC magnetic susceptibility at different magnetic field amplitudes. We discussed the flux flow regime and pinning and used the Cole-Cole plots to calculate the grain fraction in the samples. Finally, real parts was used to calculate the lower critical magnetic field H(T) as a function temperature.