Incommensurate Magnetic Structure of the Heavy Fermion Antiferromagnet Ce_7Ni_3 : Condensed Matter: Electronic Properties, etc.

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Magnetic structures of the heavy fermion antiferromagnet Ce_7Ni_3 have been studied by neutron diffraction using a single crystal. It undergoes the two successive phase transitions at T_<N1> = 1.8 K and T_<N2> = 0.7 K in zero field. At T_<N1> ordering of a single-k type magnetic structure with an incommensurate modulation vector k_<IC> ≃ 0.22c* takes place. This structure is approximately a sinusoidally modulated structure of c-axis moments, which belongs to the Γ_2 and Γ_3 irreducible representations of the space group P6_3mc. Root mean squares of the moments at T = 1.4K are 0.46±0.07, 0.70±0.03 and 0.10±0.05 μ_B for the Ce1, Ce2 and Ce3 sites, respectively. Below T_<N2> the incommensurate modulation vector becomes temperature independent, and a commensurate structure with k_C = 1/4c* appears in addition to the incommensurate structure. The metamagnetic transition under the magnetic field of H_<||c> = 0.16 T at T = 1.5 K is a first order transition to a ferromagnetic state.
社団法人日本物理学会の論文
2000-07-15