Canted antiferromagnet superimposed on a buckled kagomé network in RbMn4(PO4)3

Rubidium tetra­manganese tris­(phosphate), RbMn4(PO4)3, has been synthesized as single crystals under hydro­thermal conditions. The crystal structure was refined in the space group Pnnm (D2h12). It is argued that the size factor RM/RA, i.e. the ratio of the A+ ionic radius to the M2+ ionic radius, within the morphotropic series AM4(TO4)3 corresponds to a specific type of crystal structure. At low temperatures, the anti­ferromagnet superimposed on a buckled kagome network in RbMn4(PO4)3 experiences a transition into a long-range ordered state with finite spontaneous magnetization. First principles calculations provide the dominant magnetic exchange inter­actions both within and between the kagome layers. The analysis of these inter­actions allows us to suggest a model of alternating ferromagnetic and anti­ferromagnetic arrangements within chains of Mn3 atoms.