Structures and Magnetic Properties of KPdUS, KPtUS, RbPtUS, and CsPtUS Synthesized Using the Boron-Chalcogen Mixture Method.

A series of AMUS (A = alkali metal; M = Pd, Pt) compounds, specifically KPdUS, KPtUS, RbPtUS, and CsPtUS, were synthesized using the combined boron-chalcogen mixture and molten flux crystal growth methods. The formation of rubidium- and cesium-containing analogues resulted from a alkali polysulfide flux formed from alkali carbonates. The successful synthesis of single crystals of the title compounds allowed for their structural characterization by single-crystal X-ray diffraction. The structure determination revealed disorder of the alkali cations in RbPtUS and CsPtUS, while the potassium cations in KPdUS and KPtUS were fully ordered. Magnetic measurements were performed on samples of KPtUS, RbPtUS, and CsPtUS that contained small amounts of paramagnetic β-US and diamagnetic PtS. Antiferromagnetic order was observed at = 9.1 K for KPtUS. No long-range magnetic order was observed for RbPtUS and CsPtUS. Uranium moments of 2.5, 2.6, and 2.6 μ were measured for KPtUS, RbPtUS, and CsPtUS, respectively.