Magnetic Properties of Superconducting Vanadium

Abstract

Isothermal magnetization data were obtained for an annealed single crystal of vanadium (resistivity ratio $\frac{{\ensuremath{\rho}}_{273\mathrm{K}}}{{\ensuremath{\rho}}_{4\mathrm{K}}}=450$) in prolate spheroidal form in the temperature interval from $T=1.4$ K to ${T}_{c}(=5.43 \mathrm{K})$, which was measured to be 5.43 \ifmmode\pm\else\textpm\fi{} 0.02 K. To minimize surface pinning and increase the reversibility of the bulk magnetization, the sample surface was subjected to an oxidation treatment. Values of the thermodynamic critical field ${H}_{c}(t)$ determined from the data are in good accord with the earlier results of Radebaugh and Keesom, and the Ginzburg-Landau parameter was deduced from the measurements to be $\ensuremath{\kappa}(1)=0.85\ifmmode\pm\else\textpm\fi{}0.02$. In the limit of infinite electronic mean free path it is found that ${\ensuremath{\kappa}}_{0}=0.82$ for this sample. The temperature variations of ${\ensuremath{\kappa}}_{1}(t)$, ${\ensuremath{\kappa}}_{2}(t)$, and the parameter ${h}^{*}(t)=\frac{{H}_{c2}(t)}{{(\ensuremath{-}\frac{d{H}_{c2}}{\mathrm{dt}})}_{t=1}}$ are discussed and compared with previous work. The results tend to confirm the importance of Fermi-surface anisotropy effects in type-II superconductors in the clean limit.