Thermal Expansion of Martensitic A15 Superconductors: V₃Si

¹ Department of Physics, Monash University, Clayton, Vicotria 3168, Australia
² Vice-Chancellor's Department, La Trobe University, Melbourne 3083, Australia

Abstract

The martensite phase morphology of V3Si has been controlled by the application of appropriate stress fields to a single crystal. With this procedure, it is possible to transform the crystal to a single, tetragonal domain, enabling the thermal expansion coefficients for the tetragonal a and c axes to be measured, using high-resolution, capacitance dilatometry. Expansion anomalies were found at low temperatures, well below the superconducting critical temperature, for both the a and c axes. The tetragonality continues increasing on cooling at low temperatures, which, predicted by theory, should have been inhibited by the onset of superconductivity. In addition, anisotropy in thermal expansion is found up to 50 K, which is well above the conventional M_s temperature of 21 K.