Effect of dc field on ac-loss peak in a commercial Bi:2223/Ag tape

Abstract

Measurements of the ac susceptibility in a commercial Bi:2223/Ag tape for some different ac magnetic field amplitudes, H ac , in the presence of bias magnetic field H dc directed along H ac are reported. It is found that the peak values of the imaginary component of ac susceptibility χ″ max versus H ac trace a valley for the orientation where applied field H a perpendicular to wide face of the tape total. We note that the observation of the valley depends on various parameters such as field dependence parameter n in the critical current density, in the simple power law expression j c = α (T )/Bn , choice of the bias field H dc together with selected ac field amplitudes H ac , and dimension and geometry of sample studied. Our calculations based on critical state model with j c = α (1 − T /T cm )p /Bn using the fitting parameters of n = 0.25, p = 2.2, T cm = 108 K gives quite good results to compare the experimental and calculated curves.