2004 年 28 巻 3 号 p. 347-350
We report the Mn doping effect in FeCr2S4, which does not possess heterovalency, or static Jahn-Teller distortion, but exhibits large magnetoresistance. In order to see the effects of substituting Fe2+ for Mn2+ on the conduction, magnetism, and magnetoresistance, we carried out an experimental study of the electrical and magnetic properties of Fe0.5Mn0.5Cr2S4. FeCr2S4 has a spin-glass phase below 60 K ( = Tg) and a ferrimagnetic phase in the temperature range 60-170 K (Tc = about 170 K). In Fe0.5Mn0.5Cr2S4, both the spin-glass and ferrimagnetic transitions are observed in lower temperature regions (Tg = 45 K, Tc = 140 K). FeCr2S4 is a semiconductor, but exhibits metallic-like behavior in the temperature range 150-170 K. Fe0.5Mn0.5Cr2S4 does not exhibit such metallic behavior, but anomalous transition of the temperature dependence of resistivity is observed in the temperature range 100-180 K. Fe0.5Mn0.5Cr2S4 exhibits a larger maximum negative magnetoresistance (MR) than FeCr2S4. Thses experimental data can be well explained on the basis of the polaron model.