Exchange and relaxation of rare-earth impurities and conduction electrons in YbA12:R (R = Nd, Eu, Gd, Dy, Er)

The bottleneck phenomena in YbAl2:Gd and YbAl2:Eu is used to extract the conduction electrons' spin-flip relaxation to the lattice, deltasub(eL)sup((0)). The values observed are compared with those observed in the other dialuminides, XAl2:Gd (X = Sc, Y, La, Lu). A correlation between deltasub(eL)sup((0)) and the atomic number of the host X atom is clearly demonstrated, and is similar to that found by others for rare-earth beryllides. A simple model is suggested to explain this observed phenomenon. The ESR isothermal limit of the R ion in YbAl2 enables one to extract the dependence of the ion-conduction electron exchange coupling on the 4f occupation number. Results can shed some light on the nature of the Yb ions in YbAl2 at low temperatures. (author)