Magnetic microscopy for characterization of local critical current in iron-sheathed MgB₂ wires

We have developed a characterization method of local critical current in iron-sheathed MgB₂ wires. Local homogeneity was visualized by the scanning Hall-probe microscopy (SHPM). The value of local critical current was quantified with the aid of the finite element method (FEM) considering the ferromagnetic properties of the iron sheath. The results suggested that MgB ₂ wires fabricated by internal Mg diffusion processes still have large longitudinal inhomogeneity and much higher potential than that estimated by the four-probe transport method. This will be very important information for making a correct strategy for further development of MgB₂ wires.