Further studies of the enhanced nuclear magnet HoVO 4 - I. The crystal field and the Zeeman spectrum

Abstract

A novel approach is adopted to fit the experimental results for the Van Vleck paramagnet HoVO 4 . Within the ground manifold 5 I 8 , J = 8, the five parameters for a crystal field of tetragonal symmetry are adjusted to give values in agreement with the optical spectrum for the lowest energy levels: the ground singlet, the first excited doublet at 21 cm -1 , and the (accidental) triplet at 47 cm -1 . Within experimental error (of order 1 cm -1 ), this agreement is not impaired by a small modification in which all the crystal field parameters are multiplied by a factor 1.0225. This factor is introduced to give the correct value of the enhanced nuclear magnetic resonance frequency for the stable isotope 165 Ho ( I = 7/2), known to 0.3% (Bleaney et al. Proc. R. Soc. Lond . A 362, 179 (1978)). The optical Zeeman effect, calculated therefrom, is in good agreement with that observed experimentally for the lowest levels in magnetic fields up to 15 T, directed along the [100], [110] and [001] axes (Battison et al. Phys. Lett . A 55, 173 (1975); J. Phys . C 10, 323 (1977)).