Magnetic and transport properties of Ba6Fe8S15 and BaFe2S3: Magnetoresistance in a spin-glass-like Fe(II) system

The magnetic and transport properties of the Hong and Steinfink 1-dimension al barium iron sulfide phases BaFe2S3 and Ba6Fe8S15 were studied. The valen ce precise BaFe2S3 phase (Fe2+) is semiconducting with a nonmagnetic ground state due to strong intrachain antiferromagnetic coupling. However, short- range magnetic correlations and spin-glass-like behavior are found below 25 K, which gives rise to a magnetoresistive effect of 10% at 9 T. BaFe2S3 is a rare example of a magnetoresistive ternary sulfide. The mixed valent Ba6 Fe8S15 phase (Fe2.25+) is also a semiconductor with a nonmagnetic ground st ate. Ba6Fe8S15 shows similar spin-glass-like behavior but at a lower temper ature (T-f = 15 K). Comparisons with other tetrahedrally coordinated iron s ulfide phases and possible origins of the short-range magnetic correlations are discussed.