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

Detailed analyses of spectroscopic and temperature-dependent magnetic susceptibility data are reported for the crystal-field split energy levels of the 7FJ and 5D4 of Tb3+ in stoichiometric single crystals of ortho-aluminate TbAlO3. The spectroscopic data include absorption spectra obtained between 2940 and 480 nm from 8 to 300 K. High resolution fluorescence spectra are reported, representing transitions from 5D4 to 7F6,5,4, at a sample temperature of 85 K. Using crystal-field modeling techniques recently adapted for low symmetry systems, we have assigned all 58 experimental Stark levels within the 7FJ and 5D4 manifolds, with a fitting standard deviation of 4.5 cm−1 (3.8 cm−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 0.2 cm−1 splitting of the ground-state quasi-doublet. The susceptibility calculation also confirms the predicted ordering of states within the 7F6 multiplet manifold.