Effect of Nd4Ba2Cu2O10 addition on the pinning properties of Nd-Ba-Cu-O crystals

Abstract

Abstract We have studied the effects of Nd 4 Ba 2 Cu 2 O 10 (Nd422) on the pinning characteristics of NdBa 2 Cu 3 O 7− δ (Nd123) crystals. Like Y 2 BaCuO 5 particles in the Y–Ba–Cu–O system, the addition of Nd422 could enhance critical current density J c at lower fields. The peak field ( B pk ) and the J c value at B pk were almost independent of Nd422 contents although a slight decrease in J c at B pk was observed with increasing Nd422 contents. The normalized relaxation rate ( S ) increased for all the samples when the field exceeded B pk . The addition of Nd422 was effective in preventing a rapid increase in S above B pk . The exponent μ , defined in the collective creep model, was deduced by fitting the experimental data and was found to show strong field dependence. We found that μ changes from positive to negative at around B pk , suggesting that the flux creep mechanism is different below and above B pk .