Elastic study of electric quadrupolar correlation in the paramagnetic state of a frustrated quantum magnet $\rm Tb_{2+\it \delta}Ti_{2-\it \delta}O_7$

TL;DR

This study investigates electric quadrupolar correlations in the frustrated quantum magnet Tb2Ti2O7, revealing a long-range quadrupole order at low temperatures and a crossover to a strongly correlated state influenced by geometrical frustration.

Contribution

It provides experimental evidence of quadrupole ordering and identifies a crossover temperature indicating a strongly correlated quadrupole state in Tb2Ti2O7.

Findings

Elastic anomaly at 0.4 K indicating quadrupole order

Identification of a crossover temperature for quadrupole correlations

Evidence linking geometrical frustration to high onset temperature of correlations

Abstract

Electric quadrupolar state in a frustrated quantum magnet $\rm Tb_{2+\it \delta}Ti_{2-\it \delta}O_7$ has been studied by means of ultrasonic and magnetostriction measurements. A single crystal showed elastic anomaly at about 0.4 K, manifesting a long-range quadrupole ordering. By investigating anisotropy of the magnetoelastic responses, we found a crossover temperature for the strongly correlated quadrupole state, below which the experimental data of elastic constant and magnetostriction become qualitatively different from their calculations based on a single-ion model. We suppose that relatively high onset temperature of the quadrupole correlation compared with the transition temperature is ascribed to the geometrical frustration effect, and this correlated state seems to be responsible for the unusual properties in the paramagentic state of $\rm Tb_2Ti_2O_7$.