High-Field Specific Heat and Fundamental Superconducting Properties of the Single-Phase Type-II Superconductor V 3 Si

Abstract

The specific heat data above the upper critical magnetic field H c2 , the angular dependence of H c2 , and fundamental superconducting parameters were consequently determined. The V 3 Si sample used in this research does not exhibit the structural transition and its high quality was confirmed by the experimental results of electrical resistivity, magnetization, specific heat, and the X-ray powder diffraction measurements. The lower critical magnetic field H c1 was determined to be 3.3 kOe from magnetization measurements, enabling the estimation of the Gintzburg–Landau coherent length ξ 0 (40 Å), the London penetration depth λ 0 (447 Å) and the Gintzburg–Landau parameter κ GL (11.3). The upper critical magnetic field H c2 was found to be nearly angle-independent and equal to 21 T, as confirmed by tunnel diode oscillator (TDO) measurements. Specific heat measurements performed above and below H c2 were used to estimate the Sommerfeld coefficient, revealing a slight increase from 60 mJ/K 2 ·mol at zero magnetic field to 67 mJ/K 2 ·mol at 31.6 T. These γ-values are considerably enhanced compared with those of normal metals and conventional superconductors, indicating a high density of states (DOS) at the Fermi energy. The combination of a high DOS at the Fermi level and a high Debye temperature (544 K at 0 T) supports the relatively high superconducting transition temperature of V 3 Si (T c = 17 K). The extracted superconducting parameters indicate that V 3 Si is a Type-II s-wave superconductor in the weak-coupling limit.