Crystal structure, magnetic susceptibility, and electric resistivity of polycrystalline Ba 1− xK xVS 3− δ, Ba 1− xK xVSe 3− δ, and BaV(S,Se) 3 synthesized under high pressure

Abstract

The quasi-one dimensional hexagonal perovskites BaVS 3 and BaVSe 3 are susceptible to doping under high pressure. In this study barium was replaced with potassium, and mixed chalcogenides BaV(S,Se) 3 were stabilized at 3 GPa, in the temperature range 800–1000°C. X-ray powder diffraction diagrams of the product from the high pressure synthesis have profiles which show strong strain broadening. The potassium rich samples swiftly absorbs water in humid air. Rietveld analysis and assumption of Vegard's law indicate that selenium can replace sulfur in all ratios, while potassium only partially replaces barium. The magnetic properties of the sulfides are very sensitive to sulfur content, the selenides are rather unsensitive with respect to anion number. Stoichiometric BaVS 3 shows behavior similar to antiferromagnetism, but slight anion deficiency or potassium doping render them soft ferromagnets. Deviation from BaVS 3 stoichiometry depresses the low to high resistivity transition temperature. Replacing S with Se increases the dimensionality of the compound. The selenides without sulfur are ferromagnetic metals.