Spectroscopic investigation of holmium vanadate, HoVO4

Spectroscopic investigation into the properties of HoVO 4 has revealed interesting and unusual anomalies. These centre on the fact that the first excited doublet (at 21 cm -1 ) shows a small (2.3 cm -1 ) zero-field splitting at low temperatures. Although no phase transition has been detected in HoVO 4 , it is concluded from the experimental data that the splitting is real enough and that the symmetry at the Ho 3+ site must be lower than tetragonal. A number of effects which might be responsible for this splitting are investigated, but the origin of the splitting remains obscure.