Inelastic neutron scattering study of phonons and magnetic excitations in LaCoO${}_3$

Abstract

We have investigated the phonon and the magnetic excitations in LaCoO3 by inelastic neutron scattering measurements. The acoustic phonon dispersions show some characteristic features of the folded Brillouin zone (BZ) for the rhombohedrally distorted perovskite structure containing two chemical formula units of LaCoO3 in the unit cell. We observed two transverse optical (TO) phonon branches along (delta, delta, delta), consistent with previously reported Raman active Eg modes which show remarkable softening associated with the spin-state transition [Ishikawa et al., (Phys. Rev. Lett. 93 (2004) 136401.)]. We found that the softening takes place in the TO mode over the whole BZ. In contrast, the acoustic phonons show no anomalous softening associated with the spin-state transition. The low-energy paramagnetic scattering at 8 K is weak, increasing towards a maximum at E > 15 meV, consistent with excitation of the nonmagnetic low-spin to magnetic intermediate-spin state of Co 3+ ions.

14 pages, 7 figure

References in corpus (4)

• Evidence for orbital ordering in LaCoO3
• Spin-State Transition and Metal-Insulator Transition in La${}_{1-x}$Eu${}_x$CoO${}_3$}
• The influence of the rare earth ions radii on the Low Spin to Intermediate Spin state transition in lanthanide cobaltite perovskites: LaCoO3 vs. HoCoO3
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Cited by in corpus (2)

• Coulomb correlations intertwined with spin and orbital excitations in LaCoO${}_3$
• Spin-state transition and phase separation in multi-orbital Hubbard model