The antiferromagnetic structures of KFeS2, RbFeS2, KFeSe2, and RbFeSe2 and the correlation between magnetic moments and crystal field calculations

The ternary compounds KFeS₂, RbFeS₂, KFeSe₂, and RbFeSe₂ were prepared and their crystal structures were determined from single-crystal diffractometer data. The atomic arrangement in the isotypic compounds (space group C2/c) is characterized by tetrahedra of chalcogen atoms. Those tetrahedra are centered by iron ions and linked by edges, thus forming chains of ¹_∞FeX⁻_4/2] frameworks (X S or Se). Susceptibility measurements are reported. Neutron difraction experiments on powdered samples revealed magnetic structures in the antiferromagnetically ordered state. The magnetic moments of the iron ions shows a significant dependence of the atomic arrangement. Therefore calculations based on a simple point charge model are discussed to correlate the magnetic moments and crystal field splittings.