TY - JOUR
T1 - Structural and magnetic properties of the cobaltate series (BaSr) 4-xLa 2xCo 4O 15
AU - Garlea, V. O.
AU - Jin, R.
AU - Garlea, E.
AU - Ehlers, G.
AU - Mamontov, E.
AU - Myers, D. B.
AU - Xie, F.
AU - Custelcean, R.
PY - 2012/9/27
Y1 - 2012/9/27
N2 - We report the structural and magnetic properties of a new class of cobaltates with the chemical formula (BaSr) 4-xLa 2xCo 4O 15 (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 Co 4O 15 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.
AB - We report the structural and magnetic properties of a new class of cobaltates with the chemical formula (BaSr) 4-xLa 2xCo 4O 15 (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 Co 4O 15 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.
UR - http://www.scopus.com/inward/record.url?scp=84867010941&partnerID=8YFLogxK
U2 - 10.1103/PhysRevB.86.094434
DO - 10.1103/PhysRevB.86.094434
M3 - Article
AN - SCOPUS:84867010941
SN - 1098-0121
VL - 86
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 9
M1 - 094434
ER -