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Abstract:
The crystal structures of strontium cobalt oxychlorides of general
formula Sr2CoO3Cl (Co-1L), Sr3Co2O5Cl2 (Co-2L), and Sr4Co3O7.5Cl2
(Co-3L) have been determined from neutron powder data. The compounds
crystallize in tetragonal symmetry, space group P4/nmm (Co-1L) or I4/mmm
(Co-2L and Co-3L). Their structures are analogous to the
Ruddlesden-Popper phases of general formula Srn+1MnO2n+1. All three
structures contain layers of highly distorted CoO5Cl octahedron. The
Co-3L structure, in addition, has a layer of regular CoO6 octahedra.
Because the in-plane oxygen position of the latter is partially
occupied, some of the Co atoms adopt pyramidal coordination, with their
basal planes parallel to the c-axis. The temperature dependence of the
magnetic susceptibility is also reported. The moment per mole of Co atom
decreases with increasing number of (CoO2) layers.
