A COMPARISON BETWEEN VOLUME AND ELECTRONIC CONCENTRATION EFFECTS IN CE TRANSFORMATIONS

The crossover from magnetic to non-magnetic ground states in Ce compou nds is analysed within the competition between the on-site and inter-s ite interactions proposed by Doniach. The comparison of the evolution of the ordering temperature, as a function of pressure and alloying, w as performed in more than twenty Ce systems. This systematic shows tha t volume (Delta V) and electronic concentration (Delta Z) effects, as the driving forces for such a transformation, present different charac teristics. The maximum in the ordering temperature (T-o), predicted by the model, is only observed under Delta V effects (induced by alloyin g or by pressure) and not under Delta Z variations. This study leads t o the conclusion that the maximum in T-o cannot be considered intrinsi c to a complete magnetic to non-magnetic transformation, but rather is a consequence of the Ce-Ce spacing decrease, before the wavefunction overlap turns on the hybridization mechanism.