Structural phenomena associated with the spin-state transition in LaCoO 3

By P. Radaelli, S. Cheong. 2002

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The structural properties of ${\mathrm{LaCoO}}_{3}$ were studied by means of high-resolution neutron powder diffraction in the temperature range $5l~Tl~1000\mathrm{K}.$ Changes of the ${\mathrm{Co}}^{+3}$ spin states in this temperature interval are shown to affect not only the unit-cell volume, as previously known, but also internal parameters such as the metal-oxygen bond lengths. These data, as well as the temperature-dependent magnetic susceptibility, can be qualitatively modeled based on a three-state (low-spin, intermediate-spin, and high-spin) activated behavior, but correction terms are required for quantitative agreement. Our fits consistently indicate that the ionic radius of the intermediate-spin state (\ensuremath{\sim}0.56 \AA{}) is smaller than the low-spin/high-spin average (\ensuremath{\sim}0.58 \AA{}). We also present evidence of a third lattice anomaly, occurring around 800 K, which we attribute to the formation of oxygen vacancies.

Subfields: Condensed Matter Physics, Electronic, Optical and Magnetic Materials

View Paper: https://www.semanticscholar.org/paper/3572ac6a7ea2589b0ca3c34f9bcbad58fc029200