Optical spectroscopy of Yb_2Ti_2O_7 and Y_2Ti_2O_7:Yb~(3+) and crystal-field parameters in rare-earth titanate pyrochlores

摘要

Optical absorption spectra of the Yb_2Ti_2O_7 single crystals and luminescence spectra of the Y_2Ti_2O_7:Yb (1%) polycrystalline samples were registered at temperatures 4.2-300 K. These spectra and earlier published data on magnetic properties of Yb~(3+) ions and on the temperature dependence of the electric field gradient at Yb nuclei in Yb_2Ti_2O_7 were used to analyze the crystal-field parameters in rare-earth titanates with the pyrochlore structure. The self-consistent sets of crystal-field parameters for rare-earth ions in the 16d sites with the D_(3d) symmetry that describe satisfactory all known single-ion magnetic properties and low-energy excitations in R_2Ti_2O_7 crystals (R=Tb, Ho, Er, Tm, Yb) are presented.