Double Phase Transitions in the Heavy-Fermion System Ce_4Ni_3Pb_4 (Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties)

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We report on the measurements of magnetic susceptibility χ, electrical resistivity ρ, specific heat C, and thermopower S of Ce_4Ni_3Pb_4. This compound crystallizes in the trigonal (R3) La_4Ni_3Pb_4-type structure, in which Ce atoms occupy two inequivalent sites. Both C(T) and ρ(T) show anomalies at TM=4K and T_N=3K, respectively. On the other hand, M/B=χ(T) shows no anormaly at T_M, but exhibits a considerable increase below T_N. At 2K, a hysteresis loop of magnetization has a small spontaneous moment, 2×10^<-3>μB/Ce. With increasing magnetic field, the ferromagnetic behavior in χ(T) is suppressed and instead, a characteristic peak of an antiferromagnetic transition appears at B=1T. The weak ferromagnetism can be ascribed to the Dzyaloshinsky-Moriya interaction which may be present in Ce_4Ni_3Pb_4 without inversion symmetry. An extrapolation of the plot of C/T vs T^2 below 1K yields γ=200mJ/(Ce mol K^2). Thus, this compound is a rare example of a Ce-based compound in which a heavyfermion state survives in the weak ferromagnetic state.
社団法人日本物理学会の論文
2006-03-15