Spectroscopic study of low-energy states of KDy(MoO4)2-KY(MoO4)2 system

IR absorption spectra of the crystalline KDy(Mo)4)2 -KY(Mo)4)2 system are measured are measured in the spectral regions 10-30 cm-1 and 1200-2000 cm-1 at the temperatures 1.6 to 22 K. It is found that on substitution of Y3+ ions with the heavier Dy3+ ions in the concentration range 0<x<0.3, a quasi-local impurity mode sidebands near the quasi-local oscilaltion maximum due to anharmonicity. It is also found that quate a developed structure of the spectral density of oscillatory states is formed in the compounds KDy(MoO4)2 and KY(MoO4)2 in the low-frequecny region of the oscillatory spectrum (ν<30 cm-1)