NMR study of trialuminide intermetallics

We present a systematic study of the DO₂₂-structure trialuminide intermetallic alloys using ²⁷Al NMR spectroscopy. The quadrupole splittings, Knight shifts, and spin-lattice relaxation times on Al₃Ti, Al₃V, Al₃Nb, and Al₃Ta have been identified. Knight-shift tensors were isolated by observation of quadrupole satellite lines and fitting to the central-transition powder patterns. The results are associated with the local electronic density of states for each crystallographic site. Universally small isotropic Knight shifts and long T₁’s are consistent with low Fermi-surface densities of states indicating the importance of Fermi-surface features for the phase stability of these alloys. Larger anisotropic Knight shifts occurring at aluminum site I indicate strong hybridization at this site, and the electric-field-gradient tensors confirm the strong ab plane bonding configuration. Local-moment magnetism is found in Al₃V, yet electrically this material appears very similar to the other DO₂₂ aluminides.