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arXiv · 1209.2986

Structural and magnetic properties of the new cobaltate series (BaSr)4-xLa2xCo4O15

V. O. Garlea·R. Jin·E. Garlea·G. Ehlers·E. Mamontov·D. B. Myers·F. Xie·R. Custelcean
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Abstract

We report the structural and magnetic properties of a new class of cobaltates with the chemical formula (BaSr)4-xLa2xCo4O15 (x = 0, 0.5 and 1). These compounds crystallize in a hexagonal structure in which cobalt ions are distributed among two distinct crystallographic sites with different oxygen coordination. Three Co-O tetrahedra and one octahedron are linked by shared oxygen atoms to form Co4O15 clusters, which are packed together into a honeycomb-like network. Partial substitution of Sr and/or Ba atoms by La allows one to adjust the degree of Co valence mixing, but all compositions remain subject to a random distribution of charge. Magnetic susceptibility together with neutron scattering measurements reveal that all studied specimens are characterized by competing ferro- and antiferro-magnetic exchange interactions that give rise to a three dimensional Heisenberg spin-glass state. Neutron spectroscopy shows a clear trend of slowing down of spin-dynamics upon increasing La concentration, suggesting a reduction in charge randomness in the doped samples.

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V. O. Garlea, R. Jin, E. Garlea, G. Ehlers, E. Mamontov, D. B. Myers, F. Xie, R. Custelcean. 2012-09-13. Structural and magnetic properties of the new cobaltate series (BaSr)4-xLa2xCo4O15. https://doi.org/10.1103/physrevb.86.094434

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