Anisotropic magnetization properties of an NdBa2Cu3O7-δ single crystal

The magnetization properties of a flux-grown NdBa2CU3O7-delta (Nd123) single crystal were investigated by measuring DC magnetization hysteresis (M-H) loops in a wide temperature range (10-92 K) and for applied fields parallel (H parallel to c) and perpendicular (H parallel to a-b) to the c-axis of the sample. For both field directions, temperature-dependent fishtail peaks in the M-H loops are clearly observed at high temperatures above 70 K, and all the data could be scaled to a single master curve with the hysteresis loop width Delta M versus H plot when they are normalized with the peak field H-pk and its magnetization value Delta M-pk, respectively. This indicates that the origins of the peak effect and the pinning are identical for this temperature range. We have also found that H-pk and the irreversibility field H, scale with the reduced temperature, t = T/T-c (T-c: critical temperature), and follow the relationship H(irr)proportional to (1-t)(n) with a power n of 1.1-1.3. The anisotropy parameters gamma(pk) of H-pk (congruent to 6.8) and gamma(irr) of H-irr (congruent to 4.7) were deduced from the angular dependence of H-pk and H-irr at 88 K. We emphasize that all the present results support our proposal that the peak effect in the Nd123 originates from the localized Nd-Ba substituted regions with depressed T-c.