Localized itinerant electrons and unique magnetic properties of SrRu2O6

TL;DR

SrRu2O6 exhibits a rare combination of high Nel temperature, reduced magnetic moment, and simultaneous electron localization and itinerancy, explained by unique electronic states involving Ru hexagons.

Contribution

The paper reveals that SrRu2O6's unusual magnetic and electronic properties stem from highly localized yet itinerant electrons forming specific Ru hexagon states, supported by first principles calculations.

Findings

High Nel temperature despite quasi-2D structure

Reduced magnetic moment compared to ionic count

Electronic states localized on Ru hexagons with delocalization over six Ru sites

Abstract

SrRu2O6 has unique magnetic properties. It is characterized by a very high N\'eel 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 Ru6 hexagon, and completely delocalized over the corresponding six Ru sites, thus making the compound $both$ strongly localized and highly itinerant.