スピネル型硫化物Fe_<1-x>Mn_xCr_2S_4における巨大磁気抵抗効果(磁性体物理・超伝導)

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We report the Mn doping effect in FeCr_2S_4, which does not possess heterovalency, or static Jahn-Teller distortion, but exhibits large magnetoresistance. In order to see the effects of substituting Fe^<2+> for Mn^<2+> on the conduction, magnetism, and magnetoresistance, we carried out an experimenta1 study of the electrical and magnetic properties of Fe_<0.5>Mn_<0.5>Cr_2S_4. FeCr_2S_4 has a spin-glass pha,se below 60 K ( = T_g) and a ferrimagnetic phase in the temperature range 60-170 K (T_c = about 170 K). In Fe_<0.5>Mn_<0.5>Cr_2S_4, both the spin-glass and ferrimagnetic transitions are observed in lower temperature regions (T_g = 45 K, T_c = 140 K). FeCr_2S_4 is a semiconductor, but exhibits metallic-like behavior in the temperature range 150-170 K. Fe_<0.5>Mn_<0.5>Cr_2S_4 does not exhibit such metallic behavior, but anomalous transition of the temperature dependence of reslstlvity is observed in the temperature range 100-180 K. Fe_<0.5>Mn_<0.5>Cr_2S_4 exhibits a larger maximum negative magnetoresistance (MR) than FeCr_2S_4. Thses experimental data can be well explained on the basis of the polaron model.
社団法人日本磁気学会の論文
2004-03-01