Nuclear Magnetic Resonance Study ofAl27in NiAl

Physical Review1963Vol. 131(4), pp. 1473–1477

Abstract

The NMR of ${\mathrm{Al}}^{27}$ has been studied in two samples of the bcc ordered alloy NiAl whose atomic compositions were 48% Ni, 52% Al and 50% Ni, 50% Al. The line intensity of the first sample is accounted for by assuming all satellite transitions wiped out by quadrupolar interactions with defects. The width of the observed -\textonehalf{}\ensuremath{\rightleftarrows}\textonehalf{} transition was 4.5\ifmmode\pm\else\textpm\fi{}0.3 Oe, field- and temperature-independent, and can be almost entirely accounted for by ${\mathrm{Al}}^{27}$ dipole-dipole interactions. The second sample had an 11% greater width and 85% greater intensity, indicating contributions from satellite transitions. The Knight shift of both samples was 0.055\ifmmode\pm\else\textpm\fi{}0.005%, which is only one-third that of pure aluminum, and was independent of magnetic field and temperature. The specific heat of NiAl was measured from 2.2 to 4.2\ifmmode^\circ\else\textdegree\fi{}K, giving ${\ensuremath{\gamma}}_{\mathrm{el}}=12.6\ifmmode\times\else\texttimes\fi{}{10}^{3}$ ergs ${\mathrm{mole}}^{\ensuremath{-}1}$ \ifmmode^\circ\else\textdegree\fi{}${\mathrm{K}}^{\ensuremath{-}2}$, which is 87% of the value for pure aluminum. We conclude that the low value of the Knight shift results from a small Fermi-contact interaction at the aluminum sites for electrons at the Fermi surface and is not due to a low density of states.

Abstract

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