Localized itinerant electrons and unique magnetic properties of SrRu2O6

SrRu2O6 has unique magnetic properties. It is characterized by a very high Neel temperature, despite its quasi-two-dimensional structure, and has a magnetic moment more than twice reduced compared to the formal ionic count. First-principles calculations show that only an ideal Neel ordering in the Ru plane is possible, with no other metastable magnetic solutions, and, highly unusually, yield dielectric gaps for both antiferromagnetic and nonmagnetic states. We demonstrate that this strange behavior is the result of the formation of very specific electronic objects, recently suggested for a geometrically similar Na2IrO3 compound, whereby each electron is well localized on a particular Ru-6 hexagon, and completely delocalized over the corresponding six Ru sites, thus making the compound both strongly localized and highly itinerant.