Harmonics of the AC susceptibility for the study of I-V curves in melt grown YBCO

摘要

The measurements of the 1st and the 3rd harmonics of the AC magneticsusceptibility, performed on melt grown YBCO samples as a function of thetemperature and the external parameters (frequency and amplitude of AC magneticfield, intensity of a DC field) were studied by using the Cole-Cole plotanalysis. By considering the AC field dependence of the 3rd harmonics Cole-Coleplots, we have extracted information about the peculiar behaviour of the I-Vcharacteristics and, therefore, about the dissipative phenomena in the sample.The experimental results have been analysed with the help of both analyticaland numerical curves. In particular, the use of a phenomenological expressionfor the resistivity allowed us to reproduce the main experimental features,including the observed invariance of the area inside the Cole-Cole plots andtheir behaviour as a function of the AC field.