Local distortion in LaCoO3 and PrCoO3: EXAFS, XRD and XANES studies

Abstract

Room temperature Co K-edge extended x-ray absorption fine structure (EXAFS), x-ray absorption near edge structure (XANES) including pre-edge and x-ray diffraction (XRD) studies are carried out on LaCoO3 and PrCoO3. The Co-O, Co-La/Pr and Co-Co bond lengths are obtained from EXAFS analysis and compared with those obtained from XRD. The EXAFS analysis of data indicates that CoO6 octahedron is distorted in both LaCoO3 and PrCoO3. Such distortion is expected in orthorhombic PrCoO3 but not in rhombohedral LaCoO3. This distortion in CoO6 octahedron is attributed to Jahn-Teller active Co3+ ion in intermediate spin state in these compounds. Higher shell studies reveal that Debye-Waller (DW) factors of Co-Pr and Co-Co bonds in PrCoO3 are more in comparison to Co-La and Co-Co bonds in LaCoO3 indicating that these bonds are structurally more disordered in PrCoO3. The comparison of Co-Co bond lengths and corresponding DW factors indicates that the structural disorder plays an important role in deciding the insulating properties of these compounds. XANES studies have shown changes in the intensities and positions of different near edge features.

22 pages, 8 figures, 2 tables. To appear in J. Phys.: Condens. Matter

References in corpus (7)

• Linear-response theory and lattice dynamics: a muffin-tin orbital approach
• Structural phenomena associated with the spin-state transition in LaCoO3
• Evidence for orbital ordering in LaCoO3
• Local distortion of MnO${}_6$ octahedron in La${}_{1-x}$Sr${}_x$MnO${}_{3+\delta }$ (x = 0.1 to 0.9): an EXAFS study
• Temperature excitation of the Co3+ triplet spin-state in LaCoO3 determined by polarized neutron diffraction
• Electronic states of PrCoO${}_3$: X-ray photoemission spectroscopy and LDA+U density of states studies
• Electronic states of LaCoO${}_3$: Co K-edge and La L-edge X-ray absorption studies

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