Nuclear Quadrupole Interactions of ⁷Li and ⁵¹V in a Li₃VO₄ Single Crystal Studied by Nuclear Magnetic Resonance

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The rotation patterns of the nuclear magnetic resonances of ⁷Li (I=3⁄2) and ⁵¹V (I=7⁄2) in the nonlinear optical Li₃VO₄ single crystal were measured in two mutually perpendicular crystal planes. From these results, the quadrupole coupling constants and the asymmetry parameters at room temperature were determined for the first time as follows: e²qQ⁄h=53.68±2 kHz and η=0.169 for ⁷Li, and e²qQ⁄h=1.44±2 MHz and η=0 for ⁵¹V. The symmetry for the electric field gradient (EFG) of V ions surrounded by four oxygen atoms is higher than that of Li ions surrounded by four oxygen atoms. The principal axes of the EFG tensor are a=Y, b=Z, c=X for ⁷Li, and a=b=X, c=Z for ⁵¹V nucleus. Also, the ⁷Li and the ⁵¹V spin–lattice relaxation rates were measured, and the behavior is quite similar for both nuclei. The measured relaxation rate was found to be linear in the square of the temperature. The Raman process with a T² dependence is considered to be more effective than the direct process for nuclear quadrupole relaxation.