Effect of cutting position and cutting depth on the magnetic properties of Gd–Ba–Cu–O bulk superconductors
摘要
The critical current density Jc is a key factor determining the magnetic properties of bulk superconductors. Due to the anisotropic growth characteristics, rare-earth barium copper oxide superconductors are prone to exhibiting inhomogeneous Jc distributions. Previous studies have confirmed that Jc is higher at the grain sector boundaries and lower within the grain sector regions. To clarify the influence of this inhomogeneity on the levitation force and trapped field properties of the bulks, two single-domain gadolinium barium copper oxide bulk superconductors were longitudinally cut along either the growth sector boundary or the growth sector region at an angle of 45° relative to the growth sector boundary using a stepwise cutting method, with cutting depths of 0, 1, 2, 4, 6, and 8 mm respectively. With increasing cutting depth, the levitation forces of both samples gradually decreased. However, the levitation force of the sample cut along the growth sector region presented a relatively faster decreasing trend, which qualitatively agrees with the magnetic simulation results obtained using the finite element method. Moreover, trapped field investigations verified that the observed trend correlates with that of the levitation force. This was attributed to the differences in the magnetic flux pinning characteristics between the growth sector boundaries and the growth sector regions of the bulk superconductor, analyzed in the context of the non-ideal behavior of type-II superconductors and the mechanisms governing magnetic property generation. These findings are of great significance for improving the uniformity of rare-earth barium copper oxide bulk superconductors and optimizing the design of superconducting magnets.