Magnetic interactions and crystal field in RMg3 compounds (R = Ce,Pr, Nd)

We have carried out a study of magnetic properties, electrical resistivity and of crystal field excitations using inelastic neutron scattering, in cubic RMg₃ compounds with light rare earths R = Ce, Pr and Nd. The ground states are the Γ₇ and Γ₆ doublets for CeMg₃ and NdMg₃, which order at 3.5 and 6.5 K, respectively. PrMg₃ has the non-magnetic Γ₃ ground state and remains a Van Vleck paramagnet. The magnetic contribution to the resistivity has been separated. It allows us to evaluate the couplings between the 4f shell and the conduction band which is much larger for CeMg₃ than for the other compounds. The coupling constant Γ is negative in this case, as shown by an incipient Kondo effect in this compound.