Raman scattering of light by low-energy electronic excitations of the Tb3+ ion in the crystal KTb(WO4)2

The Raman scattering spectrum in a KTb(WO4)2 crystal is investigated in the frequency range 3–950cm−1 at temperatures 5, 80, and 300K. The symmetry of all 36 vibrational excitations predicted by group-theoretical analysis is determined. The temperature behavior of the scattering spectra indicates that there is no phase transition in the temperature interval studied. Low-energy electronic transitions are found between the levels of the ground-state multiplet F67 of Tb3+ split in a crystal field with symmetry C2. It is determined that the first excited electronic quasidoublet consists of two singlet levels with different symmetry and is separated by a quite high (∼75 cm−1) energy from the ground-state quasidoublet. The behavior of all experimentally observed levels in external magnetic fields H⊥C2 and H∥C2 is investigated. The results confirm that a virtually pure case of Ising anisotropy is realized at low temperatures and the magnet studied in the present work can be regarded as a system of two-level magn...