Kondo behavior, ferromagnetic correlations, and crystal fields in the heavy-fermion compounds Ce₃ X (X=In,Sn )

We report measurements of inelastic neutron scattering, magnetic susceptibility, magnetization, and the magnetic field dependence of the specific heat for the heavy Fermion compounds Ce₃ In and Ce₃ Sn. The neutron scattering results show that the excited crystal field levels have energies E₁ =13.2meV, E₂ =44.8meV for Ce₃In and E₁ =18.5meV, E₂ =36.1meV for Ce₃ Sn. The Kondo temperature deduced from the quasielastic linewidth is 17 K for Ce3 In and 40 K for Ce₃ Sn. The low-temperature behavior of the specific heat, magnetization, and susceptibility cannot be well described by J=1/2 Kondo physics alone, but require calculations that include contributions from the Kondo effect, broadened crystal fields, and ferromagnetic correlations, all of which are known to be important in these compounds. We find that in Ce ₃ In the ferromagnetic fluctuation makes a 10%-15% contribution to the ground state doublet entropy and magnetization. The large specific heat coefficient γ in this heavy fermion system thus arises more from the ferromagnetic correlations than from the Kondo behavior.