- Abstract MgB 2 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 (T cm, H c1, H c2, J c by the Bean model) were obtained with a SQUID magnetometer, and transport properties (T cr, H c2, resistivity and residual resistivity ratio) were measured using a standard four-lead configuration. The VI 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.