Flux pinning properties were studied for NdBa2Cu3O7-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 (Jc-B curves). For this high T region, while Jc(B,T) curves in low B followed an empirical equation from Matsushita et al. , 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 fp vs the reduced B/Birr, where Birr is the irreversibility field, indicating that dominant pinning mechanisms are different between low and high B region.
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