Issue 16, 2022

Anisotropic thermal expansion and electronic transitions in the Co3BO5 ludwigite

Abstract

The investigations of the crystal structure, magnetic and electronic properties of Co3BO5 at high temperatures were carried out using powder X-ray diffraction, magnetic susceptibility, electrical resistivity, and thermopower measurements. The orthorhombic symmetry (Sp.gr. Pbam) was observed at 300 K and no evidence of structural phase transitions was found up to 1000 K. The compound shows a strong anisotropy of the thermal expansion. A large negative thermal expansion along the a-axis is observed over a wide temperature range (T = 300–600 K) with αa = −35 M K−1 at T = 500 K with simultaneous expansion along the b- and c-axes with αb = 70 M K−1 and αc = 110 M K−1, respectively. The mechanisms of thermal expansion are explored by structural analysis. The activation energy of the conductivity decreases significantly above 700 K. Electronic transport was found to be a dominant conduction mechanism in the entire temperature range. The correlations between the thermal expansion, electrical resistivity, and effective magnetic moment were revealed and attributed to the evolution of the spin state of Co3+ ions towards the spin crossover and gradual charge-ordering transition.

Graphical abstract: Anisotropic thermal expansion and electronic transitions in the Co3BO5 ludwigite

Supplementary files

Article information

Article type
Paper
Submitted
27 Jan 2022
Accepted
23 Mar 2022
First published
06 Apr 2022

Dalton Trans., 2022,51, 6345-6357

Anisotropic thermal expansion and electronic transitions in the Co3BO5 ludwigite

N. Kazak, A. Arauzo, J. Bartolomé, M. Molokeev, V. Dudnikov, L. Solovyov, A. Borus and S. Ovchinnikov, Dalton Trans., 2022, 51, 6345 DOI: 10.1039/D2DT00270A

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