Anisotropic electromagnetic features of a grain-aligned ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{x}}$ bulk superconductor

The anisotropic electromagnetic features of a grain-aligned ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{\mathit{x}}$ bulk sample derived from a process of long-time partial melt growth were investigated by the measurements of dc magnetization (at 77 K) and ac susceptibility as a function of temperature, with the fields applied parallel and perpendicular to the c axis, respectively. The extended Bean model was further studied and applied to explain the experimental results. Upon comparison of the grain-aligned sample with pure single-crystal materials, it is concluded that, because of the existence of more effective pinning sites in the grain-aligned sample, not only its critical current density perpendicular to the c axis is improved, but the one parallel to the c axis is improved even more significantly. The anisotropy in the critical current densities in the grain-aligned sample at 77 K is at least 1 to 2 orders of magnitude smaller than in the pure single crystal. The measurement of anisotropy of ac susceptibility as a function of temperature, especially its imaginary part, shows that there are still some residues of interlayer weak links in the grain-aligned samples, but they are quite different from and far less serious than the weak links in the sintered samples.