Isolated spin 3/2 plaquettes in Na3RuO4

The crystal structure of Na3RuO4 determined by powder neutron diffraction is reported. The structure consists of isolated tetramers of edge sharing RuO6 octahedra in the ab plane, creating isolated four-member plaquettes of Ru atoms comprised of two equilateral triangles sharing an edge. Magnetic susceptibility measurements reveal an antiferromagnetic transition at ∼29 K, with image. Neutron diffraction data indicate the onset of three-dimensional magnetic ordering at 29 K.