Structural and magnetic properties of the new cobaltate series (BaSr)4-xLa2xCo4O15
Autor: | Garlea, V. O., Jin, R., Garlea, E., Ehlers, G., Mamontov, E., Myers, D. B., Xie, F., Custelcean, R. |
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Rok vydání: | 2012 |
Předmět: | |
Druh dokumentu: | Working Paper |
DOI: | 10.1103/PhysRevB.86.094434 |
Popis: | 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. |
Databáze: | arXiv |
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