Charge Ordering and Incommensurate Modulations in the Metamagnetic Layered Manganese Oxysulfide Sr 2 MnO 2 Cu 3.5 S 3
Year: 2026
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Sr 2 MnO 2 Cu 3.5 S 3 contains mixed-valent Mn ions Mn 2+/3+ in axially elongated MnO 4 S 2 octahedra connected via apical sulfide anions to copper-deficient antifluorite-type Cu 4-δ S 3 layers where δ ∼ 0.5. Copper deficiency is charge-compensated by oxidation of Mn 3d states resulting in mixed-valency. The compound is tetragonal in P 4/ mmm at ambient temperatures ( a = 4.016345(1) Å, c = 11.40708(5) Å). Below 190 K, superlattice reflections in diffraction data and an increase in resistivity, signal checkerboard charge-ordering of Mn 2+ and Mn 3+ . The superstructure approximates to a √2 a × √2 a × 2 c expansion of the room temperature cell in space group P 4 2 / nmc . However, satellite reflections signal a (3 + 2)D incommensurate modulation of Cu site occupancies in the Cu-deficient sulfide layers coupled with displacements of the sulfur positions; overall the superstructure below 190 K requires description in superspace group P 4 2 / nmc ( a,0,0)0000(0, a,0)00s0. Analysis of total scattering measurements along with pair distribution functions supports the charge-ordered low temperature model and reveals local order of distinct Mn sites within the higher-temperature charge-disordered regime. Below T N = 27 K, long-range magnetic ordering is A-type antiferromagnetic with distinct moments for Mn 2+ and Mn 3+ ions directed perpendicular to the MnO 2 planes and ordered ferromagnetically. Long-range antiferromagnetic order results from interlayer antiferromagnetic coupling. A metamagnetic transition at 1.1 T corresponds to a change to long-range interlayer ferromagnetic ordering via a spin-reorientation of magnetic moments and is associated with a slight decrease in the charge separation between the Mn sublattices, consistent with observations on mixed-valent perovskite and Ruddlesden–Popper-type oxide manganites.
DOI: 10.1021/jacs.5c21494
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
Awards: EPSRC Centre for Doctoral Training in Inorganic Chemistry for Future Manufacturing (OxICFM), A SQUID Magnetometer for Quantum Materials, superconductors, molecular magnets and excited states, Exploiting the anion Chemistry of solids for Future Advanced Functional Materials: Core-to-Core Project on Mixed Anion Research for Energy Conversion, A single-crystal X-ray diffractometer for the structural analysis of molecular compounds, macromolecules and materials
OpenAlex ID: W7124431222