Magnetic properties of Au-doped YBCO superconductors studied by low field AC susceptibility

We have reported a detailed study that investigates the grain boundary and the inter-granular effects on the AC susceptibilities of Au-doped YBCO superconductor as a function of temperature and doping fraction. The microstructure is obtained from scanning electron microscopy, while for the elemental analysis, we have used energy dispersive X-ray fluorescence. AC susceptibility is measured as a function of temperature in the range (40-100) K at different AC magnetic field amplitudes between 159 and 796 A/m at 500 Hz for magnetic properties. From the ac susceptibility measurements, we have studied the diamagnetic shielding behavior of AuyYBa2Cu3O7-x samples with y = 0, 1, 5, and 20 wt. %. We have also studied the normalized relation between the imaginary and the real parts of the susceptibility (Cole-Cole plot) for all the samples. We have analyzed our Tp vs. Hac data with the M & uuml;ller critical state model and chi '' vs. Hac data with the Bean state model. From these analyses, the volume fraction of grains and pinning forces is estimated. The Bean state model was found to explain our experimental findings satisfactorily.