Zeeman Studies on Er3+ in GdCl3

The absorption spectrum of Er3+ in GdCl3 has been investigated. Extensive Zeeman series have been obtained for three different groups of states with fields applied parallel to the hexagonal axis. It is found that the Zeeman splittings of the Er3+ states depend on the magnetic ordering of the GdCl3 host, and this must be considered in order to get correct Zeeman factors for these states. An attempt was made to represent the effect of the magnetic ordering on the states by a term proportional to the crystal magnetization. A theoretical expression is given for the magnetization of GdCl3 under the different conditions of temperature and field used in the experiments. The Er3+ Zeeman factors obtained with the model are seen to be consistent at all field intensities and to be in reasonable agreement with what one obtains from calculations using the crystal-field parameters of Er3+ in GdCl3.