Magnetic and vibrational properties of the covalent chain antiferromagnet RbFeS₂

Ternary rubidium-iron sulfide, RbFeS 2 , belongs to a family of quasi-one-dimensional compounds with the general chemical composition A Fe Ch (where – K, Rb, Cs, Tl; S, Se). Understanding magnetic properties these is challenge. The controversy concerning spin-state iron ion needs be resolved build proper model magnetism. Single crystals were grown and characterized by powder x-ray diffraction. QD MPMS-5 SQUID magnetometry was used measure susceptibility, specific heat measured utilizing PPMS-9 setup. Above transition three-dimensional antiferromagnetic order at Néel temperature T N = 188 susceptibility exhibits unusual quasi-linear increase up highest 500 K. in range 1.8 300 Ab initio phonon dispersion density-of-states calculations performed means density functional theory (DFT), calculated lattice subtracted from one giving contribution heat. Our results suggest that features are for whole covalent chain ternary chalcogenides structure indicate an intermediate S 3/2 spin state ion.