Crystal and magnetic structure ofLaTiO3:Evidence for nondegeneratet2gorbitals

The crystal and magnetic structures of ${\mathrm{LaTiO}}_3$ have been studied by x-ray and neutron-diffraction techniques using nearly stoichiometric samples. We find a strong structural anomaly near the antiferromagnetic ordering $T_N=146\mathrm{}\mathrm{K}.$ In addition, the octahedra in ${\mathrm{LaTiO}}_3$ exhibit an intrinsic distortion, which implies a splitting of the $t_{2g}$ levels. Our results indicate that ${\mathrm{LaTiO}}_3$ should be considered as a Jahn-Teller system where the structural distortion and the resulting level splitting are enhanced by the magnetic ordering.