1
660
A. Demont et al. / Journal of Solid State Chemistry 184 (2011) 1655–1660
exchanges must be weaker as they have to be via super-exchange
starting from freshly prepared Sr
4
3 x
Co3ꢀx(CO ) O10ꢀ4x samples. The
(
Co–O–O–Co).
crystal chemistry of such a solid solution will give the opportunity
to study the structural evolution depending on oxygen stoichio-
metry/carbonate content and its reactivity in air. All this work is
in progress. Additional neutron diffraction data at low tempera-
tures will be also needed to be more affirmative about the
magnetic behavior depending on the carbonate content and the
fine oxygen stoichiometry.
The magnetic behavior has been studied by measuring mag-
netization (M) as a function of T. The corresponding ZFC and FC
curves exhibit a complex evolution with a main peak at 50 K and
several others kinds at 160, 210 and 250 K beyond which the both
curves start to merge (Fig. 8a). A fit from Curie–Weiss law in the
temperature domain ranging from 300 to 400 K lead to
m
meffꢁ5.7
þ2.86
B/Co in agreement with the expected value for Co
high spin
deduced from structural analyses. According to the
¼M/H) and to the corresponding p (
w
low values
p¼ ꢀ520 K), the low
(
w
y
y
Acknowledgments
temperature transition could indicate an antiferromagnetic state.
For comparison, the properties of perovskite and intergrowths
related cobalt oxides are reported in Table 3. The AFM behavior
observed here is characteristic of these cobaltites with cobalt
valency close to 2.8–2.9. For all of them, a ferromagnetic compo-
nent is also observed as here in the oxycarbonate compound
The authors are grateful to Prof. M. Daturi for the IR measure-
ments and the fruitful discussions.
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