Nmr of¹⁶⁵ho in the ising ferromagnet ho(Oh)₃

The nmr spectrum of holmium has been studied, at 1.3 K, in ferromagnetic holmium hydroxide (T_c = 2.54 K). The measured hyperfine parameters are shown to pertain to the ionic ground state, not to a thermal average over ground and excited states. The dipolar splitting is in excellent agreement with crystal-field parameters derived from optical spectroscopy. The ratio of nuclear to electronic antishielding factors for Ho³⁺ derived from the quadrupolar splitting is y_N/y_E = 152 ± 10.