27Al NMR study in UNiAl

The ternary compound UNiAl exhibiting an antiferromagnetic order below T_N = 19.3 K has been studied in the paramagnetic state using the ²⁷Al NMR technique and different magnetically oriented samples. The quadrupole coupling constant e²qQ/h = 1.56 MHz is temperature independent. The dominant, longitudinal component of the Knight shift with respect to the hexagonal c axis, K, is positive and increases upon lowering the temperature down to 50 K. Much smaller in magnitude, the transverse component, K_±, is also positive and only slightly temperature dependent. The plots of the Knight shift vs magnetic susceptibility K(χ) and K_±(χ_±) form the same line, which implies that the transferred hyperfine field of 9.2 kOe/μB for ²⁷Al nuclei should be considered isotropic.