Evidence for orbital ordering in LaCoO3

We present powder and single crystal X-ray diffraction data as evidence for a monoclinic distortion in the low spin (S=0) and intermediate spin state (S=1) of LaCoO3. The alternation of short and long bonds in the ab plane indicates the presence of eg orbital ordering induced by a cooperative Jahn-Teller distortion. We observe an increase of the Jahn-Teller distortion with temperature in agreement with a thermally activated behavior of the Co3+ ions from a low-spin ground state to an intermediate-spin excited state.Comment: Accepted to Phys. Rev.

Effect of ionic size on the orbital ordering transition in RMnO3+delta

We present high-temperature powder x-ray diffraction data of the orbital-order-induced structural distortion of RMnO3, with R a rare earth element. The associated phase transition takes place in a temperature interval of ≈200K in which the orbitally ordered phase and the orbitally disordered phase coexist. We analyse the evolution of the RMnO3 perovskite structure with the size of the rare-earth ion and with temperature. We show that the rotation of the MnO6 octahedra stabilizes the cooperative Jahn–Teller distortion to higher temperature.

Morphology and surface structure of silver carboxylates

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