Spectroscopic and magnetic susceptibility analyses of the 7FJ and 5D4 multiplet manifolds of Tb3+(4f8) in TbAlO3

Full text: Detailed analyses of spectroscopic and temperature-dependent magnetic susceptibility data are reported for the crystal-field split energy levels of the 7FJ and 5D4 multiplet manifolds of Tb3+ in stoichiometric single crystals of ortho-aluminate TbAlO3. The spectroscopic data include absorption spectra obtained between 2940 nm and 480 nm from 8K to 300K. High resolution fluorescence spectra are reported, representing transitions from 5D4 to 7F6,5.,4, at a sample temperature of 85K. The energy for individual Stark levels within each manifold can be determined by common energy difference methods that are applied to the analyses of the absorption and fluorescence data. Using crystal-field modeling techniques that have been adapted recently for low symmetry systems, we have assigned all 58 experimental Stark levels within the 7FJ and 5D4 manifolds, with a fitting standard deviation of 4.5cm-1 (3.8cm-1 rms error). As a further test, the theoretical Stark levels and calculated wavefunctions were used to determine the temperature dependence of the magnetic susceptibility along the c axis of the TbAlO3 crystal. Good agreement is obtained between the calculated susceptibility and temperature-dependent magnetic data reported earlier, including a prediction of a 0.2cm-1 splitting of the ground-state quasi-doublet. The susceptibility calculation also confirms the predicted ordering of states within the 7F6 multiplet manifold. (authors)