The a.c. magnetization characteristics of NdBa2Cu3Oy (Nd123) bulk superconductors were investigated using a.c. susceptometry. For the present study, an OCMG-processed Nd123 bulk sample (OCMG-Nd123; Tc = 93.9 K) and a flux-grown Nd123 single crystal (Nd123SC; Tc = 93.2 K) were used. An MPMG-processed Y123 bulk sample (MPMG-Y123; Tc = 91.6 K) was also studied for comparison. While the fundamental responses are basically the same for all samples, the third harmonic responses by sweeping the bias field, X3(Hdc), show an interesting feature in that the X3(Hdc) curves for Nd123 samples indirectly reflect the fishtail peak of their d.c. magnetization hysteresis (M-H) curves. The boundary lines of Nd123 samples, determined from both the peak temperature (Tp) of the X1″(T) maxima and the offset of the X3(Hdc), are commonly located at higher field-temperature region relative to that of the Y123. Using the scaling relationship of H∝(1 - t)n, where t = T/Tc, all the boundary lines from the X3(Hdc) and the X1″(T) maxima could be best fit with a power n of ∼ 1.2 and ∼ 1.4, respectively.
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