Equilibrium Curve and Entropy Difference between the Supraconductive and the Normal State in Pb, Hg, Sn, Ta, and Nb

摘要: The thermodynamical treatment of supraconductivity (Gorter and Casimir 1934 a, b ) is based on the fact that at transition from normal into supraconductive state induction becomes zero it was assumed magnetic threshold curve, i. e. curve in ( H, T diagram indicates disappearance electric resistance, also equilibrium between state. It has to be remembered, however, resistance are not causally connected by electrodynamic theory, but their coincidence must as yet considered a purely empirical fact. therefore possible deduce existence observation vice versa. is, for example, known do coincide alloys (Mendelssohn 1935) preliminary experiments tantalum Moore 1936) have shown even pure metals values obtained conductivity cannot used an evaluation quantities. In two previous communications (Keeley Mendelssohn 1936; methods (later called 1 2) determination supraconductors were described. With these curves extremely Pb, Hg, Sn, Ta, Nb determined temperature interval 1·5° 4·2° K.