Optical spectroscopy ofYb2Ti2O7andY2<

Abstract

Optical absorption spectra of the Yb 2 Ti 2 O 7 single crystals and luminescence spectra of the Y 2 Ti 2 O 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 2 Ti 2 O 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 2 Ti 2 O 7 crystals (R = Tb, Ho, Er, Tm, Yb) are presented.

Neutron spectroscopic study of crystalline electric field excitations in stoichiometric and lightly stuffedYb2Ti2O7

“…This suggests negligible precession around this easy axis and thus strong Ising-like behavior. The local magnetization anisotropy for the Asite Yb 3+ in the presence of a single O(1) oxygen vacancy is dramatically different from the stoichiometric case, where it was planar or XY-like 39,40,44 , and is similar to that displayed by the prototypical spin ice magnets Dy 2 Ti 2 O 7 and Ho 2 Ti 2 O 7 . This anisotropy is present even without the B m n ratio corrections and thus it depends only on the depleted environment.…”

Static magnetic susceptibility, crystal field and exchange interactions in rare earth titanate pyrochlores

“…The sets of CFP used in calculations are presented in table 1. Earlier the CFP for rare earth titanates were estimated in the framework of the exchange charge model [28]. In the present work, the results of these calculations have been corrected to fit the available spectral data and the measured temperature dependence of the dc-susceptibilities.…”

“…Our attempts to describe the crystal field energies of the Yb 3+ (4f 13 ) ions in Yb 2 Ti 2 O 7 determined from optical spectra [28] and the recently observed temperature dependence of the longitudinal site susceptibility χ [27,29] by making use of a single set of CFP have failed. The g value for the ground doublet determined from the experimental results presented in [27,29] [25].…”

“…Parameters of the crystal field Hamiltonian operating in the space of states of the ground 5 I 8 multiplet of the Ho 3+ ions were determined earlier in [28,45]. In the current work, we started from these parameters and obtained a more accurate parameter set (see table 1) from the fitting procedure based on computations of the thermal averages (9) and (10) with the effective Hamiltonian (2) operating in the total space of 1001 states of the 4f 10 configuration.…”

“…To facilitate a detailed comparison of the results of calculations with experimental data, the dcsusceptibility of single crystalline Tb, Ho, Gd and Dy titanate was measured in the temperature range 2-300 K (section 3). Anisotropic single ion susceptibilities were computed using sets of crystal field parameters (CFP) obtained from calculations in the framework of the exchange charge model [28] and from a systematic analysis of the available data on spectral and magnetic properties of rare earth titanate pyrochlores. Parameters of the anisotropic exchange interaction between the nearest neighbor R 3+ (R = Gd, Tb, Dy, Ho, Er) ions have been determined through fitting the calculated bulk and site susceptibilities (section 4) to the experimental data.…”