Crystal-field parameters of the rare-earth pyrochlores R2Ti2O7 (R=Tb, Dy, and Ho)

In this work, we present inelastic neutron scattering experiments which probe the single ion ground states of the rare-earth pyrochlores R2Ti2O7 (R=Tb, Dy, Ho). Dy2Ti2O7 and Ho2Ti2O7 are dipolar spin ices, now often described as hosts of emergent magnetic monopole excitations; the low-temperature state of Tb2Ti2O7 has features of both spin liquids and spin glasses, and strong magnetoelastic coupling. We measured the crystal-field excitations of all three compounds and obtained a unified set of crystal-field parameters. Additional measurements of a single crystal of Tb2Ti2O7 clarified the assignment of the crystal-field levels in this material and also revealed an example of a bound state between a crystal-field level and an optical phonon mode.