Magnetization of Synthetic Filamentary Superconductors. B. The Dependence of the Critical Current Density on Temperature and Magnetic Field

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Abstract
Measurements of the magnetization of cylinders of synthetic high‐field superconductors were made as a function of magnetic field and temperature. The superconductors were made by impregnating porous glass with indium. The porous glass can be characterized by the pore diameter; the critical field and the transition temperature depend strongly on the pore diameter. Assuming a critical‐state model, the current density Jc was calculated from the magnetization versus field curves and was found to be of the form Jc=A−CB for magnetic fields B less than 0.3 of the critical field. In greater fields, Jc is almost independent of field. A and C depend upon temperature. For values of the ratio T/Tc between 0.9 and 0.5, A increases linearly with decreasing temperature. Several samples with different pore sizes have been measured; no systematic dependence on pore size was found.