Superconductivity at High Magnetic Fields

摘要: Using pulsed-magnetic-field techniques, we have studied the magnetic-field-induced superconducting transitions of alloys in systems Ti-V, Ti-Nb, Ti-Ta, Ti-Mo, Zr-Nb, Hf-Nb, Hf-Ta, U-Nb, and U-Mo. For concentrated low-current-density resistive critical field ${H}_{r}(J\ensuremath{\lesssim}10 \mathrm{A}/{\mathrm{cm}}^{2})$ is nearly independent amount cold working relative orientations magnetic field, current, anisotropic defect structure. The observed values ${H}_{r}(J=10)$ peak up sharply (reaching 145 kG Ti-Nb system) vicinity \ensuremath{\sim}4.5 "valence" electrons per atom, an electron concentration where peaking also typically occurs for such (approximately) defect-independent transition metal alloy parameters as temperature, thermodynamic electronic specific heat coefficient. All above evidence suggests that these determined principally by bulk parameters, rather than nature extended lattice defects. This view further supported observation that, several Group V-rich, IV-Group V alloys, excellent quantitative agreement achieved adjustable-parameter-free comparisons with ${H}_{c2}$, "upper field" predicted on basis Ginzburg-Landau-Abrikosov-Gor'kov (GLAG) theory case negative surface energy. certain ranges composition, it appears normal-state paramagnetic free-energy considerations, ignored GLAG theory, impose limitations good accord theoretical predictions Clogston. Additional experimental results are reviewed, argued a comprehensive understanding high-field superconductivity materials may be modified to include terms, consider transport supercurrents stabilized manner similar suggested Gorter Anderson. priori assumptions Mendelssohn's filamentary-mesh model appear, other hand, inadequate suitable description.