Far infrared optical properties of the pyrochlore spin ice compound Dy₂Ti₂O₇

Abstract

Abstract. Near normal incident far-infrared reflectivity spectra of [111] dysprosium titanate (Dy 2 Ti 2 O 7 ) single crystal have been measured at different temperatures. Seven phonon modes (eight at low temperature) are identified at frequency below 1000 cm −1 . Optical conductivity spectra are obtained by fitting all the reflectivity spectra with the factorized form of the dielectric function. Both the Born effective charges and the static optical primitivity are found to increase with decreasing temperature. Moreover, phonon linewidth narrowering and phonon modes shift with decreasing temperature are also observed, which may result from enhanced charge localization. The redshift of several low frequency modes is attributed to the spin-phonon coupling. All observed optical properties can be explained within the framework of nearest neighbor ferromagnetic(FM) spin ice model.

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

“…The crystal field energies presented above do not agree with frequencies of the extra modes (87, 132, 158, 270 cm −1 ) observed in the low temperature Raman spectrum of Sm 2 Ti 2 O 7 and ascribed to electronic excitations (crystal field modes) [3]. In any case, only two crystal field modes with frequencies less than 10 3 cm −1 may be observed, and it is more likely that the observed extra modes correspond to IR active phonons (see [47]) which become Raman active due to crystal inhomogeneities.…”

Temperature‐dependent Raman scattering studies of the geometrically frustrated pyrochlores Dy2Ti2O7, Gd2Ti2O7 and Er2Ti2O7

“…It is worth noting that recently temperature dependence of infrared modes of Dy 2 Ti 2 O 7 was studied which also revealed softening of a number of modes with decreasing temperature. 44 This behavior was attributed to the spin-phonon coupling. Our results give, however, strong evidence that at least at higher temperatures the softening of phonons in this class of materials can be attributed to the phonon-phonon coupling, instead of spin-phonon coupling.…”

Temperature-dependent Raman and x-ray studies of the spin-ice pyrochloreDy2Ti2O7and nonmagnetic pyrochlore

“…In the temperature-dependent infrared studies of Dy 2 T i 2 O 7 in ref [15] the phonon anomalies have been attributed to the spin-phonon coupling. Our quantitative measurements of the phonon frequency for various modes in the spin-ice Dy 2 T i 2 O 7 ( Fig.…”

“…Recently, vibrational properties of some titanate pyrochlores (including the spin-ice Dy 2 T i 2 O 7 ) have been studied using infrared reflectivity [15] and Raman spectroscopy [16,17] up to room temperature. In the work by Maczka et al [17] on R 2 T i 2 O 7 (R = Er, Gd and Dy), Raman studies of Gd 2 T i 2 O 7 and Er 2 T i 2 O 7 were carried out to determine the temperature dependence of Raman mode frequencies and line-widths.…”