Indirect evidence for exchange modification of the conduction bands in RAl2 compounds

The self-polarization contribution to the total hyperfine field at a rare-earth nucleus should be directly correlated with a variation in the hyperfine splitting parameter as seen by the 4f electron of the rare-earth ion. Comparison of data on the hyperfine field in ordered ErAl2 and DyAl2 with paramagnetic resonance results for Er and Dy in ScAl2, LuAl2, and YbAl2 suggests that the self-polarization effect is large in the ferromagnetic phase but negligible in the paramagnetic phase. Analysis of available data on some Pr and Tm compounds also suggests self-polarization effects to be negligible in the paramagnetic phase. We conclude that modification of the conduction-electron band structure due to exchange splitting effects may play an important role in the rare-earth--Al2 compounds