Localized-itinerant dichotomy and unconventional magnetism in SrRu(2)O(6)

Electron correlations tend to generate local magnetic moments that usually order if the lattices are not too frustrated. The hexagonal compound SrRu(2)O(6) has a relatively high Neel temperature but small local moments, which seem to be at odds with the nominal valence of Ru(5+) in the [Formula: see text] configuration. Here, we investigate the electronic property of SrRu(2)O(6) 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. SrRu(2)O(6) 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.