Abstract
A15-type Nb/sub 3/Al has been characterized in the recent past as a ''high-T/sub c/, low-..gamma.. superconductor,'' where ..gamma.. is the electronic specific-heat coefficient. We show that this statement should be revised, previous analyses simply reflecting the imperfect metallurgical state. We succeeded in preparing homogeneous, nearly stoichiometric, bulk Nb/sub 3/Al and reinvestigated the specific heat (from 1 to 50 K) and the magnetic susceptibility (19--300 K) in the highly ordered and a slightly disordered condition. The new results show that ordered Nb/sub 3/Al exhibits a high electronic density of states (..gamma.. = 11.4 mJ K/sup -2/ g-at./sup -1/, N(0)approx. =0.91 eV/sup -1/ atom/sup -1/ spin/sup -1/). Information is provided on the moments of the phonon spectrum and those of the electron-phonon spectral function, the thermodynamical critical field, and the energy gap 2..delta..(0). The present experiments further establish only weak exchange enhancement of the susceptibility; spin fluctuations may therefore be safely neglected. Specific-heat data are also reported for the neighboring sigma-phase Nb/sub 2/Al.
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