The origin of the non-Fermi liquid state on heavy-fermion Ce compounds

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In accordance with the plans,(1) Single crystals, Ce(Ru_<1-x>Rh_x)_2Si_2 for x = 0.4, 0.5 and 0.6, were made.(2) An ac susceptibility measurement system was made, which works in the temperature range down to 50 mK and in the magnetic field up to 6 T.We found the ac susceptibilities under magnetic fields χ(T,H) can be expressed by the scaling law as the following.χ(T,H) = T^γf(H/T^δ) (T<1K, H<0.1T)The values of indexes γ, δ of x = 0.5 are different from those of x = 0.6. The scaling law suggests the origin of the non-Fermi liquid behavior in Ce(Ru_<1-x>Rh_x)_2Si_2 is the critical phenomena of the phase transition at T = 0 K. The spin at Ce atom in the mixed compound has good Ising character due to the doublet ground state and has a high Kondo temperature, and the disorder due to the Rh substitution is introduced. Quantum Griffiths phase at T = 0 K can be expected under such a situation. Our results strongly suggest the origin of the non-Fermi liquid behavior is the critical phenomena of the phase transition to quantum Griffiths phase at T = 0 K.