Flux pinning properties of NdBa₂Cu₃O_7-d single crystals flux-grown in low oxygen partial pressures

Flux pinning properties were studied for NdBa₂Cu₃O_7-d (Nd123)single crystals flux-grown in low oxygen partial pressures. In the high temperature (T) region roughly above 70 K, apparent fishtail peaks were commonly observed on the magnetization hysteresis (M-H) curves or the critical current density vs magnetic field (J_c-B curves). For this high T region, while J_c(B,T) curves in low B followed an empirical equation from Matsushita et al. [1], those in high B obviously deviated from the equation, however, those could be well scaled to a single curve by plotting the normalized flux pinning force density f_p vs the reduced B/B_irr, where B_irr is the irreversibility field, indicating that dominant pinning mechanisms are different between low and high B region.