First principles calculation and experimental investigation of lattice dynamics in the rare earth pyrochlores R2Ti2O7 (R=Tb, Dy, Ho)

TL;DR

This study combines density functional calculations with various scattering experiments to accurately characterize the lattice dynamics and phonon spectra of rare earth titanate pyrochlores R2Ti2O7, aiding understanding of their magnetic properties.

Contribution

It provides a validated model of phonon modes in R2Ti2O7 using combined theoretical and experimental approaches, enhancing understanding of spin-lattice interactions in these materials.

Findings

Good agreement between calculations and experiments for phonon energies and symmetries.

Identification of phonon modes across the Brillouin zone for R=Ho.

Estimation of phonon density of states for R=Tb, Dy, Ho.

Abstract

We present a model of the lattice dynamics of the rare earth titanate pyrochlores R2Ti2O7 (R=Tb, Dy, Ho), which are important materials in the study of frustrated magnetism. The phonon modes are obtained by density functional calculations, and these predictions are verified by comparison with scattering experiments. Single crystal inelastic neutron scattering is used to measure acoustic phonons along high symmetry directions for R=Tb, Ho; single crystal inelastic x-ray scattering is used to measure numerous optical modes throughout the Brillouin zone for R=Ho; and powder inelastic neutron scattering is used to estimate the phonon density of states for R=Tb, Dy, Ho. Good agreement between the calculations and all measurements is obtained, allowing confident assignment of the energies and symmetries of the phonons in these materials under ambient conditions. The knowledge of the phonon spectrum is important for understanding spin-lattice interactions, and can be expected to be transferred readily to other members of the series to guide the search for unconventional magnetic excitations.