LAUSR

Recently synthesized Ba4NbMn3O12 belong to cluster magnets that are systems with tightly bound groups of magnetic ions, in this case Mn3 trimers. Such magnetic clusters can often be described by molecular orbitals, however strong electron correlations may invalidate this description. To understand the electronic and magnetic state of Ba4NbMn3O12 we carried out ab initio calculations and show that this system is better described not in molecular orbitals picture, but as a system with electrons localized on the Mn ions, with strong intracluster and weaker inter-cluster exchange. The calculated spin of the Mn3 trimer is S = 2, in agreement with the experiment. The predicted magnetic structure of Ba4NbMn3O12 is that of ferromagnetic layers of Mn3 trimers, stacked antiferromagnetically.