Magnetic properties of a quaternary iron sulfide BaLa2FeS5

The magnetic properties of a quaternary iron sulfide BaLa2FeS5 have been investigated through AC and DC magnetic susceptibility and specific measurements. The effective magnetic moment of the Fe ion was found to be 5.41μB in the temperature range where the Curie–Weiss law holds good. This result indicates that the divalent Fe ions are in a high-spin (S=2) state. The zero-field-cooled condition (ZFC) magnetic susceptibilities have a maximum at 22 K and decrease with decreasing temperature, while the field-cooled condition (FC) susceptibilities are nearly constant below 22 K. The magnetic specific heat has a broad maximum at 28 K. In the AC magnetic susceptibilities, single maxima of χ′ and χ″ are observed at around 25 K. The frequency dependence of the corresponding peak temperatures of BaLa2FeS5 can be described as a thermally activated process for spin-glasses.