Paramagnetism of Tin Observed at the Superconducting Transition

概要

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Measurements have been made of the paramagnetism of tin cylinders in the presence of an external magnetic field and with an externally supplied current at the superconducting transition. It has been ascertained that the paramagnetic effect is not such an apparent one as once supposed, but an intrinsic one without hysteresis. The current minimum I_0, required for the appearance of a paramagnetic effect is represented in the (I-H-T) space by the simultaneous equations I_0=ξd(T_c-T) and H_0=ξT_c-T)-I_g/γd. Here I_g, γ, T_c and ξare characteristic constants of the superconductor and have values 1.2 amp, 0.23, 3.73°K and 1.1×10^2 oersted/deg respectively for the case of tin. H_0 and d are the external magnetic field in cersted and the specimen diameter in mm respectively. It is shown that the formula, I_0 = I_g + γdH obtained by earlier investigators for the minimum current requirement is the one for the orthogonal projection on the. (I-H) plane of the critical line in the (I-H-T) space. The paramagnetic region is shown schematically in the (I-H-T) space. Finally some remarks concerning the theory of the paramagnetic effect are given.
東北大学の論文