Comparative study of magnetic phase diagrams of Ce compounds

Thermal properties of magnetically ordered Ce-lattice systems are compared in their crossover to the non-magnetic state, driven by alloying effects. The ordering temperature (T-ord=T-N or T-C) is found to go to zero continuously only in a few cases, while in others a discontinuity in its decrease is clearly observed. Coincidentally, the magnetic contribution to the specific heat (C-p), the entropy and the free energy variations with temperature mark an evident difference between those cases. Furthermore, the extension of the non-fermi-liquid (NFL) phase in terms of concentration variation correlates with differences observed in the respective ordered phase. A systematic transformation from a mean field like transition to a fluctuation dominated type is observed in C-p(T), as the system overcomes a characteristic crossover concentration. Such a concentration appears as a limit for the NFL behavior in the paramagnetic phase above T-ord. A possible origin of the mentioned differences are discussed in terms of some alternatives in the evolution of the magnetic moments and the strength of their interactions.