Magnetization analysis of QMG YBa2Cu3O7-delta by using the Kim-Anderson critical state model

A sample of the YBa2Cu3O7-delta superconductor was prepared by using the qu ench-melt-growth process. Full magnetization hysteresis loops were measured , for H parallel to c, as a function of the temperature and the magnetic fi eld. The hysteresis loops were fitted to the Kim-Anderson critical state mo del for the entire range of temperatures. From the results of the fitting, we obtained the superconducting parameters, the lower critical field H-c1, the surface barriers DeltaH, and the full penetration field H-p, at each te mperature point. This model describes the M(H) curves very well for 77K, at which the peak effect disappears, and above.