Continuous Evolution from Kondo Lattice to Impurity Kondo Regime in Ce_1-xLa_xFeGe₃

抄録

A gradual change from the Kondo lattice to the impurity Kondo regime has been observed in Ce_1-xLa_xFeGe₃ (x=0, 0.1, 0.3, 0.5, 1.0). CeFeGe₃ exhibits a greatly reduced resistivity below about 100, K corresponding to the coherent state of the Kondo lattice. Ce_0.5La_0.5FeGe₃, on the other hand, shows a resistance minimum around 30K which is consistent with the impurity Kondo regime. The ground state of CeFeGe₃ turns out to be very stable against the La substitution and no magnetic instability is induced in the present diluted system.Magnetic susceptibility at 0, K per mole of Ce, χ (0), and the linear term of the specific heat, γ increase by 24% and 15% from x=0.0 to 0.5, respectively. The Kondo temperatures T_K's estimated from χ (0) and γ decrease accordingly by 20 and 13% in the same range of La content. This decrease in T_K is explained by the lattice expansion caused by the substitution of La for Ce.