Anomalous Magnetic and Transport Properties in Ce_2Fe_<17> and Lu_2Fe_17

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Using single phased Ce_2Fe_<17> and Lu_2Fe_<17> with the rhombohedral Th_2Zn_<17>-type and Th_2Ni_<17>-type structure, respectively, we performed measurements of magnetization and resistivity under various magnetic field up to 5.5 T.Ce_2Fe_<17> exhibits a simple helical spin structure with a wave vecter ofτ=0.0372 Å^<-1> parallel to the c-axis in the temperature range of T_c= 125K <T<T_N = 210 K. For T<T_c, it shows a modified helix of τ=0.0435Å^<-1> parallel to the c-axis with a superstructured magnetic cell, in which the magnetic c-parameter is twice as large as the chemical unit cell. Only below T_c, a giant magnetoresistance is induced by a metamagnetic transition from the helix to ferromagnetic phase in the field of H<2T. The value of Δρ/ρ ( = (ρ_<AF>-ρ_F)ρ_<AF>) reaches 0.85 at 4.2K. Such GMR may be atributed to the suppression of a super-zone gap induced by a formation of the superstructured magnetic cell below T_c. On the other hand, GMR could not be observed in Lu_2Fe_<17>.
社団法人日本磁気学会の論文
1999-01-20