AC MAGNETIZATION CHARACTERISTICS OF ND123 BULK SUPERCONDUCTORS

The a.c. magnetization characteristics of NdBa2Cu3Oy (Nd123) bulk supe rconductors were investigated using a.c. susceptometry. For the presen t study, an OCMG-processed Nd123 bulk sample (OCMG-Nd123; T-c = 93.9 K ) end a flux-grown Nd123 single crystal (Nd123SC; T-c = 93.2 K) were u sed. An MPMG-processed Y123 bulk sample (MPMG-Y123; T-c = 91.6 K) was also studied for comparison. While the fundamental responses are basic ally the same for all samples, the third harmonic responses by sweepin g the bias field, chi(3)(H-dc), show an interesting feature in that th e chi(3)(H-dc) curves for Nd123 samples indirectly reflect the fishtai l peak of their d.c, magnetization hysteresis (M-H) curves. The bounda ry lines of Nd123 samples, determined from both the peak temperature ( T-p) of the chi(1) ''(T) maxima and the offset of the chi(3)(H-dc), ar e commonly located at higher field-temperature region relative to that of the Y123. Using the scaling relationship of H proportional to(1 - t)(n), where t = T/T-c, all the boundary lines from the chi(3)(H-dc) a nd the chi(1) ''(T) maxima could be best fit with a power n of similar to 1.2 and similar to 1.4, respectively. (C) 1997 Published by Elsevi er Science Ltd.