Crystal field parameters of the rare earth pyrochlores $R_2$Ti$_2$O$_7$ ($R$ = Tb, Dy, Ho)

TL;DR

This study uses inelastic neutron scattering to determine the crystal field parameters of rare earth pyrochlores R2Ti2O7 (R=Tb, Dy, Ho), revealing insights into their magnetic states and a novel bound state between crystal field levels and phonons.

Contribution

It provides a unified set of crystal field parameters for R2Ti2O7 compounds and identifies a new bound state between a crystal field level and an optical phonon.

Findings

Unified crystal field parameters for all three compounds.

Identification of a bound state between crystal field level and phonon.

Clarification of crystal field level assignments in Tb2Ti2O7.

Abstract

In this work we present inelastic neutron scattering experiments which probe the single ion ground states of the rare earth pyrochlores $R_2$Ti$_2$O$_7$ ($R$ = Tb, Dy, Ho). Dy$_2$Ti$_2$O$_7$ and Ho$_2$Ti$_2$O$_7$ are dipolar spin ices, now often described as hosts of emergent magnetic monopole excitations; the low temperature state of Tb$_2$Ti$_2$O$_7$ 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 Tb$_2$Ti$_2$O$_7$ clarified the assignment of the crystal field levels in this material and also revealed a new example of a bound state between a crystal field level and an optical phonon mode.