The specific heat of superconducting mercury, indium and thallium

Abstract

The application of thermodynamics to the transition between the superconducting and normal states in the presence of a magnetic field yields formulae by which the entropy difference and specific heat difference of the two states may be determined from measurements of the threshold magnetic field (Gorter and Casimir 1934). These determinations involve the deduction of the first and second derivatives of the threshold field curve. They have been made for a number of superconductors (Daunt and Mendelssohn 1937; Daunt, Horseman and Mendelssohn 1939) and in the case of tin the agreement with direct specific heat measurements is good (Keesom and van Leer 1938). The usual process of differentiating twice by visually determining the tangents to the curves, however, introduces a considerable experimental error.