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

Journal Article · Sun Jan 01 00:00:00 EST 2012 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.86.094434· OSTI ID:1068079

Garlea, Elena ^[1]; Garlea, Vasile O ^[1]; Ehlers, Georg ^[1]; Mamontov, Eugene ^[1]; Custelcean, Radu ^[1]; Jin, R. ^[2]

---

1. ORNL
2. Louisiana State University

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 dierent 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 spindynamics upon increasing La concentration, suggesting a reduction in charge randomness in the doped samples.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1068079
• Journal Information: Physical Review B, Vol. 86, Issue 9; ISSN 1098--0121
• Country of Publication: United States
• Language: English