Structural and magnetic properties of the cobaltate series (BaSr)(4-x)La2xCo4O15

Article

关键词: CRYSTAL-STRUCTURE;    STATE;    TRANSITIONS;    YBACO4O7;    DYNAMICS;    CHARGE;    LN;   

DOI  :  10.1103/PhysRevB.86.094434

来源: SCIE

【 摘 要 】

We report the structural and magnetic properties of a new class of cobaltates with the chemical formula (BaSr)(4-x)La2xCo4O15 (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 honeycomblike 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.

【 授权许可】

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