Spin dynamics and orbital state in LaTiO3

A neutron scattering study of the Mott-Hubbard insulator LaTiO3 (T-N = 132 K)reveals a spin wave spectrum that is well described by a nearest-neighbor superexchange constant J = 15.5 meV and a small Dzyaloshinskii-Moriya inte raction (D = 1.1 meV). The nearly isotropic spin wave spectrum is surprisin g in view of the absence of a static Jahn-Teller distortion that could quen ch the orbital angular momentum, and it may indicate strong orbital fluctua tions. A resonant x-ray scattering study has uncovered no evidence of orbit al order in LaTiO3.