Some thermal and magnetic properties of tantalum, niobium, and vanadium at helium temperatures

Measurements of the thermal conductivity of tantalum, niobium, and vanadium in the normal and superconducting states were made using specimens of various chemical purities and crystalline states. The difference between annealed monocrystals and strained polycrystals is discussed and the contribution in the superconductive state of the lattice waves at temperatures below one-sixth of the transition temperature is clearly shown. The thermal resistance in the intermediate state was measured for the purest monocrystals of tantalum and niobium, and the critical field curve for a monocrystal of tantum was determined. (auth)