Evidence for Jahn-Teller distortions at the antiferromagnetic transition in LaTiO$_3$

TL;DR

This study provides evidence of Jahn-Teller distortions and orbital order at the antiferromagnetic transition in LaTiO$_3$, based on comprehensive structural, thermal, and spectroscopic measurements.

Contribution

It presents new experimental evidence linking Jahn-Teller distortions to the antiferromagnetic transition in LaTiO$_3$, highlighting structural changes associated with orbital order.

Findings

Structural changes at $T_N$ are volume conserving.

Anomalies observed in resistivity, bulk modulus, and optical spectra.

Evidence supports the presence of orbital order at the transition.

Abstract

LaTiO$_3$ is known as Mott-insulator which orders antiferromagnetically at $T_{\rm N}=146$ K. We report on results of thermal expansion and temperature dependent x-ray diffraction together with measurements of the heat capacity, electrical transport measurements, and optical spectroscopy in untwinned single crystals. At $T_{\rm N}$ significant structural changes appear, which are volume conserving. Concomitant anomalies are also observed in the dc-resistivity, in bulk modulus, and optical reflectivity spectra. We interpret these experimental observations as evidence of orbital order.