Cluster Magnetism of Ba4NbMn3O12: Localized Electrons or Molecular Orbitals?

详细

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.