Sr₅Os₃O₁₃: a mixed valence osmium(v,vi) layered perovskite variant exhibiting temperature dependent charge distribution

Abstract

New Sr 5 Os 3 O 13 , as synthesized from binary constituents, exhibits several uncommon features. Its crystal structure is dominated by quasi-2D poly-oxoanions that correspond to unprecedented cutouts of the perovskite type of structure, where corner sharing (OsO 6 ) octahedra aggregate to form terraced slabs.The Os 5+ /Os 6+ mixed valence oxide displays a particular charge ordering scheme. One osmium atom (Os1) per formula unit is in the valence state of 5+ in the whole temperature range studied, while the two remaining sites (Os2A and Os2B) show full charge disorder at high temperatures, resulting in an average charge of 5.5+. The latter, however, apparently undergo a process of continuous charge ordering at cooling. Full charge order appears to be established concomitantly with a phase transition to an antiferromagnetically ordered state at T (Néel) = 170 K. This kind of temperature dependent continuous charge ordering is reflected by structural changes with temperature as well as by changes in paramagnetic response above T (Néel) . Disentangling the intimate interplay between magnetic and charge ordering degrees of freedom will require applying sophisticated spectroscopy and (neutron) diffraction techniques.

Quantum materials with strong spin–orbit coupling: challenges and opportunities for materials chemists

“…Another intriguing example is the Os 5+ /Os 6+ mixed oxide Sr 5 Os 3 O 13 , which shows complex temperature-dependent behaviour. 113 In this material, one of the three osmium sites remains Os 5+ across a wide temperature range, but the other two sites seem to show charge-ordering that varies continuously down to the Néel temperature, at which point full charge-order locks in alongside antiferromagnetic ordering. Precisely determining both the oxidation states present and whether they are ordered, clustered or disordered is key to understanding the structures and magnetism of these materials but is non-trivial, often requiring facility-based techniques such as X-ray absorption spectroscopy (XAS).…”

Study of Polycrystalline Bulk Sr3OsO6 Double-Perovskite Insulator: Comparison with 1000 K Ferromagnetic Epitaxial Films

“…14 Moreover, a small anomaly is detected at ~12 K with thermal hysteresis, suggesting a glassy transition or FM transition. It should be noted that Sr5Os3O13, 31 Sr2Os3O5, 32 and Sr7Os4O19 32 have been synthesized in the ternary system Sr-Os-O, but none of them displays a magnetic anomaly at ~12 K. To conduct a quantitative analysis, the Curie-Weiss law 1/χ = (T-θW)/C was applied to fit to the curve above ~200 K, where θW is the Weiss temperature and C is the Curie constant. The estimated θW and C are -47.0(5) K and 0.638(2) emu mol -1 K, respectively.…”

“…14 Moreover, a small anomaly is detected at ∼12 K with thermal hysteresis, suggesting a glassy transition or FM transition. It should be noted that Sr 5 Os 3 O 13 , 31 Sr 2 Os 3 O 5 , 32 and Sr 7 Os 4 O 19 32 have been synthesized in the ternary system Sr−Os−O, but none of them displays a magnetic anomaly at ∼12 K.…”

New Sr9Os5O23, Made Up of Quasi 1D and 2D Fragments of the Perovskite Structure

“…Ternary and quaternary osmates continue to attract distinct attention for their pertinent physical properties by virtue of manifestations of spin−orbit coupling (SOC), Hund's coupling, and Coulomb correlation operating on similar energy scales. Respective observations have revealed, e.g., reduced effective paramagnetic moments, 4−9 temperature dependent charge order, 10 high magnetic ordering temperature, 11−13 or unusual S = 0 state of Os 6+ . 14,15 High temperature synthesis of ternary osmates has remained an intricate endeavor due to the multitude of phases existing in the same phase space and accessible within a short-range of temperature 1000−1300 K. While the synthesis in air only works for quaternary osmates and a few ternary osmates with Os in high oxidation states (+6, +7), 4,9,16,17 the preparation of osmates with intermediate valence of Os (+4, +5, and +6) requires a closed environment.…”

“…Interestingly, the crystal structure of this compound is built up of the exact excerpts from the Sr 5 Os 3 O 15 and Sr 2 OsO 5 structures. 10,21 The osmium here is in a mixed-valence state (+5/+6). Use of…”