The ability of RP-type cobaltites to accommodate carbonate groups: A new layered oxide Sr4Co2(CO3)O5.86

The possibility to introduce carbonate groups inside a pure cobalt based Ruddlesden Popper type matrix is demonstrated. This paper reports the synthesis as a single phase of a new layered oxycarbonate Sr4Co2(CO3)O5.86 and its structural characterizations at room temperature combining TEM observations and powder neutron diffraction data. Close structural relationships are observed with the homologous Sr4Fe3−x(CO3)xO10−4x series and deal with the presence of two specific carbonate configurations, namely coat hanger and flag. Magnetization measurements reveal a complex antiferromagnetic behavior below 50 K with three others transitions, at 160, 210 and 250 K. Such behavior can be ascribed to the latent reactivity in air of this largely oxygen deficient phase.