Localized-itinerant dichotomy and unconventional magnetism in SrRu₂O₆

Electron correlations tend to generate local magnetic moments that usually order if the lattices are not too frustrated. The hexagonal compound SrRu₂O₆ has a relatively high Neel temperature but small local moments, which seem to be at odds with the nominal valence of Ru⁵⁺ in the [Formula: see text] configuration. Here, we investigate the electronic property of SrRu₂O₆ using density functional theory (DFT) combined with dynamical-mean-field theory (DMFT). We find that the strong hybridization between Ru d and O p states results in a Ru valence that is closer to +4, leading to the small ordered moment ~1.2 μ _B . While this is consistent with a DFT prediction, correlation effects are found to play a significant role. The local moment per Ru site remains finite ~2.3 μ _B in the whole temperature range investigated. Due to the lower symmetry, the t _2g manifold is split and the quasiparticle weight is renormalized significantly in the a _1g state, while the renormalization in [Formula: see text] states is about a factor of 2-3 weaker. Our theoretical Neel temperature ~700 K is in reasonable agreement with experimental observations. SrRu₂O₆ is a unique system in which localized and itinerant electrons coexist with the proximity to an orbitally-selective Mott transition within the t _2g sector.