Superconducting nanowire fiber mats and the paramagnetic Meissner effect

Superconducting nanowire fiber mats of Bi2Sr2CaCu2O8, YBa2Cu3O7 and GdBa2Cu3O7 were fabricated using electrospinning and solution blow-spinning. Fiber mats consisting of individual nanowires with long lengths (∼100 µm) and diameters between 150 and 500 nm were obtained. Magnetic properties of the samples were measured by SQUID magnetometry. Having studied a large number of such samples, we find that only the YBCO fiber mats exhibit the paramagnetic Meissner effect (PME), whereas the other materials do not. To explain these observations, we regard the current flow through the nanowires, the distinctly different current densities and the vortex dimensionality at temperatures close to Tc.