COMPETITION BETWEEN THE SCREENING EFFECT AND EXCHANGE INTERACTIONS INTHE SYSTEM S-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.25)(X (0)

Magnetic measurements on three alloys in the series CeCu1-xAl3+x (X = 0, 0.16, 0.25) reflect the increasing strength of exchange interaction s with Al concentration. As determined by ac susceptibility measuremen ts, the Neel temperatures are 2.5, 2.7 and 3.3 K for the three samples x = 0, 0.16 and 0.25, respectively. Specific data for CeCuAl3 show th at the entropies associated with the magnetic ordering accounts for on ly approximately 40% of the theoretically expected Rln2 entropy. The s ubstitution of Cu by Al in CeCu1-xAl3+x, which increases the average c onduction electron density, seems unable to attenuate the localized Ce -4f moments. These results suggest that the RKKY interactions surpass the tendency of the conduction electrons to screen the Ce-4f moments i n this system.