Optical spectroscopy study of KDy(WO4)2: Crystal-field levels of Dy3+ and the Jahn-Teller transition

Transmission spectra of a double potassium-dysprosium tungstate KDy(WO4)(2) single crystal in the region of intermultiplet transitions of the Dy3+ ion and the Raman spectra of light scattering on the electronic levels of the H-6(15/2) ground multiplet of Dy3+ are studied in a wide temperature range. The energy scheme for the crystal-field (CF) levels of Dy3+ in KDy(WO4)(2) is created. The phase transition at the temperature 6.3 K is accompanied by the lowering of the energy of the ground Dy3+ CF state, which is evidenced by both the transmission and Raman spectroscopies. Splitting of the low-lying (& SIM;13 cm(-1)) first excited CF level of the Dy3+ ion indicates the simultaneous structural phase transition. The role of Davydov interaction is discussed.