Non-Fermi Liquid-Like Behavior in a Heavy Lanthanide Compound YbFe_4P_<12> with Filled Skutterudite Structure Probed by ^<31>P-NMR(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We have carried out ^<31>P-NMR study on a new intermediate-valence compound YbFe_4P_<12> with a filled skutterudite structure which has heavy fermion-like properties below〜10K. The Knight shift has a very small value less than 0.05%, and the linewidth exhibits a monotonic increase without exhibiting any singular behavior down to 0.5K. The nuclear spin-lattice relaxation rate 1/T_1T below〜50K strongly depends on both the temperature T and applied magnetic field H and follows the power-law relation 1/T_1T=AT^<-α> over one decade. The power α〜0.1 at 7.0T increases with decreasing H and takes the maximum value of ≃ 0.7 at 0.2T, which is close to the value 3/4 expected for the non-Fermi liquid (NFL) state associated with antiferromagnetic spin fluctuations. We suggest that YbFe_4P_<12> is an interesting material in which the NFL-like behavior occurs below a rather high temperature of〜10K, and a magnetic field of about 0.2T is sufficient to bring it to its quantum critical point.
2006-06-15