The irreversible magnetic behavior at various temperatures of an ex situ Fe-alloy/MgB2 wire, exhibiting a granular compositional distribution, was studied by using an in-field, high-resolution Hall probe imaging system. Quantitative information about the local current density was obtained by solving the Biot–Savart inversion problem. The flux penetration and current distribution maps obtained could be attributed to an inhomogeneous compositional so-called plum-cake-like system, consisting of large isolated MgB2 agglomerations embedded in a matrix of finely distributed MgB2+MgO. The critical current densities within the grains and their evolution with applied magnetic field and temperature were obtained, and compared to the mean JC(H,T) in the matrix.

Critical Current Density Analysis of ex situ MgB2 Wire by In-Field and Temperature Hall Probe Imaging. E.Bartolomé, X.Granados, V.Cambel, J.Fedor, P.Kovác, I.Husek: Superconductor Science and Technology, 2005, 18, 1135-40