A Comparison of the Magnetic Structures of KMn4(PO4)3 and KCo4(PO4)3 Based on the Connectivity of the Coordination Polyhedra

The crystal structures of KMn4(PO4)(3) and KCo4(PO4)(3) have been determined by, neutron diffraction at room temperature. Both compounds are orthorhombic with similar cell parameters. but they crystallize in different space groups, Pnam for the Mn phosphate and Pnnm for the Co analogue. On the basis of the metal cation polyhedra and their connectivity, the crystal structures have been rationalised. which allow interpretation of the main magnetic interactions between them. Magnetic measurements show ferromagnetic behaviour for the Co compound, whereas in the Mn derivative antiferromagnetism is observed. Both magnetic structure are described and qualitatively analysed in terms of superexchange and super-super exchange interactions.