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Issue 44, 2014
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Triple CoII, III, IV charge ordering and spin states in modular cobaltites: a systematization through experimental and virtual compounds

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Abstract

The series of modular compounds [BanCo2+nO3n+2][BaCo6O9] (n = 1 to 3) including experimental and hypothetical terms, was investigated using DFT calculations and several experimental results. A systematic evolution of the electronic and magnetic states was evidenced along the series leading to ordered CoII/CoIIIversus mixed CoIII/IV charge segregation in two distinct structural motifs. In essence, using different packing modes within the labile [BanCo2+nO3n+2] block, we have systematized the spin state dependence on the CoO6 connectivity, i.e. corner-sharing (HS states) against face-sharing (LS states). We also show that the electronic and magnetic features of the [BaCo6O9] blocks do not vary trough the series, (i.e. HS-CoII and LS-CoIII charge ordering) whereas the [BanCo2+nO3n+2] blocks hold drastic changes from n = 1 to 3. In particular, the later carries a mixed III/IV cobalt charge for n ≥ 2. It leads to a triple valence cobalt state. For n = 2, we experimentally observe at 4 K a superstructure (2a, 2c) superstructure accompanied by a perfect CoII/CoIII/CoIV charge ordering. The charge ordering occurs at Tt = 160 K and is accompanied by a transition in the electronic transport leading to a 2D-VRH behaviour below Tt.

Graphical abstract: Triple CoII, III, IV charge ordering and spin states in modular cobaltites: a systematization through experimental and virtual compounds

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Publication details

The article was received on 09 Jul 2014, accepted on 21 Sep 2014 and first published on 24 Sep 2014


Article type: Paper
DOI: 10.1039/C4TC01486C
Author version available: Download Author version (PDF)
Citation: J. Mater. Chem. C, 2014,2, 9457-9466
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    Triple CoII, III, IV charge ordering and spin states in modular cobaltites: a systematization through experimental and virtual compounds

    R. David, H. Kabbour, P. Bordet, D. Pelloquin, O. Leynaud, M. Trentesaux and O. Mentré, J. Mater. Chem. C, 2014, 2, 9457
    DOI: 10.1039/C4TC01486C

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