One-dimensional, mixed-metal sulphides – structural and physical properties

摘要

New one-dimensional sulphides based on Ba2CoS3 have been synthesised and their structural and electronic properties investigated. The starting point was the one-dimensional sulphide Ba2CoS3, which shows one-dimensional anti-ferromagnetism, metallic-like behaviour and a small negative magnetoresistance. Cationic substitutions were carried out on both the barium and cobalt sites of Ba2CoS3. The substitution of zinc for cobalt into Ba2CoS3 resulted in the formation of the series Ba2Cox1−xZnxS3 (x = 0.0-1.0). Ba2Co1−xZnS3 compounds maintain the one-dimensional structure but become paramagnetic and show semiconducting properties. Interestingly significant values of magnetoresistance (up to −25%) are found in the series. The origin of the magnetoresistance is currently unknown although it is suspected that there is some extrinsic contribution. The compound Ba2Co0.75Fe0.25S3 has also been successfully synthesised although attempts to form compounds with higher iron content were not successful. A large number of compounds in the series Ba2Zn1–xMxS3 (M = Fe, Mn, Cr, Ni) have also been synthesised and initial investigations into the properties of these materials show that again they exhibit negative magnetoresistance. Finally Ba1.9K0.1CoS3 has been synthesised although no investigation into the properties has yet been carried out.