The Superconductivity of Columbium

Abstract

Isothermal critical magnetic field curves and zero field transitions for several annealed specimens of columbium have been measured by an a.c. mutual inductance method, at temperatures from 5.1°K to the zero field transition temperature. The $H-T$ curve was found to fit the usual parabolic relationship $H=H_0(1-\frac{T^2}{T_0^{}{}_{}{}^2})$ with $H_0=8250\mathrm{}$ oersteds and $T_0=8.65\mathrm{}$°K. The initial slope of the curve was 1910 oersteds/deg. The electronic specific heat in the normal state calculated from the thermodynamic equations is $0.0375T$ and the approximate Debye characteristic temperature in the superconducting state, 67°K. Results on a different grade of columbium with a tantalum impurity of 0.4 percent, according to neutron scattering measurements, were in agreement with the data obtained from columbium of 0.2 percent maximum tantalum impurity.