L 10,9 multiplet manifolds of Tb 3+ ͑4f 8 ͒ in D 2 sites in cubic garnet Tb 3 Ga 5 O 12 ͑TbGaG͒ are investigated at sample temperatures between 1.8 K and room temperature. Absorption measurements extend from 5000 to 340 nm. From analyses of temperature-dependent ͑hot-band͒ absorption spectra, many of the crystal-field split energy ͑Stark͒ levels of the 2S+1 L J multiplet manifolds of Tb 3+ are identified and confirmed from analyses of the fluorescence spectra observed between 485 and 680 nm, representing transitions from the 5 D 4 to the 7 F J manifolds. Each manifold is split by the crystal field into 2J + 1 Stark levels. Some of these manifolds, including the ground-state manifold 7 F 6 , consist of Stark levels that are accidentally degenerate, or nearly so, making transitions to or from these levels appear as unresolved spectra, even at the lowest temperature investigated ͑1.8 K͒. To resolve these spectra, we have investigated the Zeeman and magneto-optical spectra for representative manifolds 5 D 4 , 7 F 5 , and 7 F 6 at temperatures of 78 and 85 K and magnetic fields up to 7 kOe. The data are interpreted using the Stark levels and wave functions from a crystal-field splitting calculation that involved 80 individual Stark levels identified from the optical spectra of the 7 F J and quintet states reported in this study. Good agreement is obtained between the calculated and the experimental Stark levels. The calculated energy and symmetry label for each Stark level in the 5 D 4 , 7 F 5 , and 7 F 6 manifolds suitably interpret the spectral properties observed in the magneto-optical spectra, including the experimental assignment reported in the literature for the ground state as a quasidoublet ͕⌫ 1 , ⌫ 2 ͖.

In the region of the A1g6(S6)→A1g4,Eg4(G4) optical transition, the absorption spectrum of the quasi-two-dimensional antiferromagnet MnPS3 has an exciton-magnon structure. It includes a pure exciton line with a wave number of 21223.5cm−1 and an exciton-magnon band with a peak at 21328cm−1 for T=1.7K. The spectra are studied at temperatures ranging from 1.7to80K and with external magnetic fields up to 60kOe. In a magnetic field oriented along the easy axis z, splitting of the exciton line is observed owing to the nonequivalence of the magnetic sublattices with respect to an external field. The behavior of the split components in the region of the spin-orientation transition (35–41kOe) is typical of second order phase transitions.

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