  MgB2 superconducting wires were produced by the Mg diffusion method. Scanning
electron microscopy (SEM), optical microscopy, dispersive x-ray analysis (EDS)
and XRD diffraction were used to study the physical structure and content of
the wires. Magnetic properties (Tcm, Hc1, Hc2, Jc by the Bean model) were
obtained with a SQUID magnetometer, and transport properties (Tcr, Hc2,
resistivity and residual resistivity ratio) were measured using a standard
four-lead configuration. The V-I characteristics of the wires close to the
critical temperature showed a staircase response, which was attributed to the
presence of weak links, creating phase slip centers. The origin of those weak
links is discussed in relation to their formation and structure.
