Single crystal ²⁷Al-NMR study of the cubic Γ₃ ground doublet system PrTi₂Al₂₀

We report results of ²⁷Al-NMR measurements on a single crystal of PrTi₂Al₂₀, in which the ground state of Pr³⁺ ions in the crystalline electric field is the nonmagneitc Γ₃ doublet. From the analysis of NMR spectra with the magnetic field applied precisely along the 〈111〉 and 〈100〉 directions, we determined the electric field gradient tensors for all three inequivalent Al sites (Al(1) ∼ Al(3) sites) and the anisotropic Knight shifts for the Al(3) sites. The hyperfine coupling tensor at the Al(3) sites is strongly anisotropic and much larger than the classical dipolar coupling, indicating importance of the anisotropic hybridization between the conduction and ƒ electron states. (paper)