Presence of 3d Quadrupole Moment in LaTiO3 Studied by 47,49Ti NMR

TL;DR

This study uses Ti NMR spectra to reveal a significant 3d quadrupole moment in LaTiO3, challenging the orbital liquid model and supporting an orbital ordering model with quenched orbital moments.

Contribution

It provides experimental evidence of a large 3d quadrupole moment in LaTiO3, refuting the orbital liquid model and supporting an orbital ordering model based on crystal field effects.

Findings

Large nuclear quadrupole splitting observed in NMR spectra.

Quadrupole moment of 3d electrons at Ti sites is significant.

Orbital moment is mostly quenched in LaTiO3.

Abstract

Ti NMR spectra of LaTiO3 are reexamined and the orbital state of this compound is discussed. The NMR spectra of LaTiO3 taken at 1.5 K under zero external field indicate a large nuclear quadrupole splitting. This splitting is ascribed to the presence of the rather large quadrupole moment of 3d electrons at Ti sites, suggesting that the orbital liquid model proposed for LaTiO3 is inappropriate. The NMR spectra are well explained by the orbital ordering model expressed approximately as $1/\sqrt{3}(d_{xy}+d_{yz}+d_{zx})$ originating from a crystal field effect. It is also shown that most of the orbital moment is quenched.