Superconductivity of Indium-Thallium Solid Solutions

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Abstract
Measurements are reported on the superconducting properties of indium-thallium solid solutions in the composition range from pure indium to 50 percent thallium. The magnetic induction and the electrical resistance were measured at various temperatures and magnetic field strengths. Single crystal specimens of composition 0, 5, 10, 15, and 20 atom percent thallium, and polycrystalline specimens containing 15, 20, 38, and 50 percent thallium, were investigated. In the more dilute solutions the penetration of field into the specimen at constant temperature was sharp and the restoration of resistance occurred at substantially the same field. As the concentration of thallium increased, the flux penetration occurred over a wider range of field and the resistance appeared only after practically all the flux had penetrated. For the single crystal specimens the trapped flux in zero field was less than 20 percent of that corresponding to unit permeability at the field where flux penetration begins. The breadth of transition in the polycrystalline specimens was like that of the single crystals, but the trapped flux was much larger. The critical fields for destruction of superconductivity are given for the range 0 to 20 percent thallium and the electronic heat capacities of the normal metal are calculated from them.