Lattice Disorder And Size-Induced Kondo Behavior in CeAl(2) And CePt(2+X)

When the particle size of CeAl{sub 2} and CePt{sub 2+x} samples is reduced to the nanometer scale, antiferromagnetism is suppressed and Kondo behavior dominates. We find that the Kondo temperature T{sub K} can either decrease (CeAl{sub 2}) or increase (CePt{sub 2+x}) in the nanoparticles relative to the bulk. Extended x-ray absorption fine-structure data show that the Ce-Al and Ce-Pt environments are significantly distorted in the nanoparticles. While such distortions should strongly affect magnetic and electronic properties, we find they cannot explain the observed changes in T{sub K}. Changes in the conduction density of states or other parameters must, therefore, play a significant role.