Phonons and magnetic excitations in the Mott insulator LaTiO3 -: art. no. 172301

The polarized Raman spectra of stoichiometric LaTiO3 (T-N=150 K) were measured between 6 and 300 K. In contrast to earlier report on half-metallic LaTiO3.02, neither strong background scattering nor Fano shape of the Raman lines was observed. The high-frequency phonon line at 655 cm(-1) exhibits anomalous softening below T-N: a signature for structural rearrangement. The assignment of the Raman lines was done by comparison to the calculations of lattice dynamics and the nature of structural changes upon magnetic ordering is discussed. The broad Raman band, which appears in the antiferromagnetic phase, is assigned to two-magnon scattering. The estimated superexchange constant J=15.4+/-0.4 meV is in excellent agreement with the result of neutron-scattering studies.