Thermal and transport properties of Hf1-xTaxFe2

We report the results of specific-heat and electrical-resistivity measurements of Hf1-xTaxFex, which show a magnetic transition from a ferromagnetic (F) to an antiferromagnetic (AF) state with increasing temperature at x=0.2. A sharp peak was observed in the specific-heat curve of x=0.2 at 140 K. The corresponding entropy change due to the F-AF transition is estimated as 1.2 J/K mol. The electronic-specific-heat coefficient γ and the coefficient of the T2 term in the resistivity, A, are very enhanced in the AF state due to spin fluctuations. Topological frustration is proposed as an origin of spin fluctuations. It was found that the Laves-phase compounds with strong spin fluctuations satisfy the Kadowaki-Woods relation A/γ2=1.0×10-5 μΩ cm(K mol/mJ)2 as well as the heavy-fermion systems do. The results are discussed on the basis of spin-fluctuation theory.