Spin-state equilibria in holmium cobaltate

Bhide, V. G. ; Rajoria, D. S. ; Reddy, Y. S. ; Rama Rao, G. ; Rao, C. N. R. (1973) Spin-state equilibria in holmium cobaltate Physical Review B, 8 (11). pp. 5028-5034. ISSN 0163-1829

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Official URL: http://prb.aps.org/abstract/PRB/v8/i11/p5028_1

Related URL: http://dx.doi.org/10.1103/PhysRevB.8.5028


Mossbauer and magnetic susceptibility studies of HoCoO3 have shown that there is coexistence of low-spin Co(III) ions and high-spin Co3+ ions; Co(III) being more predominant at low temperatures. The population of Co(III) and Co3+ equalizes above a particular temperature with these ions occupying alternate oxygen octahedra, leading to an ordered phase. The ordering transition is evidenced by the temperature variation of Lamb-Mossbauer factor, x-ray Debye-Waller factor, and inverse susceptibility. Electrical-conductivity data reflect these changes in the spin-state equilibria and show that at around 1080 K, HoCoO3 becomes metallic. At this temperature, a first-order localized electron-collective electron transition seems to occur. Co(II) and Co4+ are not formed by electron transfer from Co3+ to Co(III) as in LaCoO3. This behavior is correlated with the variation of covalency in the cobaltates.

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Source:Copyright of this article belongs to American Physical Society.
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