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Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Superconducting Screening On Different Length Scales In High-Quality Bulk Mgb2 Superconductor, J. Horvat, Saeid Soltanian, Alexey Pan, Xiaolin Wang
Saied Soltanian
High-quality bulk MgB2 exhibits a structure of voids and agglomeration of crystals on different length scales. Because of this, the superconducting currents percolate between the voids in the ensuing structure. Magnetic measurements reveal that the superconducting currents circulate on at least three different length scales, of ∼1 μm, ∼10 μm, and whole of the sample (∼millimeter). Each of these screenings contributes to the measured irreversible magnetic moment (Δm). The analysis of the field dependence of Δm for samples of subsequently decreasing size showed that the critical current obtained using the simple critical state model is erroneous. This leads to the …