Holmium-ion dynamics in Ho/sub x/Lu/sub 1-x/Rh4B4

For the last several years the study of rare-earth (RE) Rh4B4 compounds has provided a rich source of information regarding the interplay of magnetic and superconducting phenomena. Discovered by Mathias and co-workers, the ferromagnetic, superconducting, and paramagnetic phase boundaries are by now well known. In addition, a set of crystal-field parameters recently has been determined that gives a general overall accounting of the magnetization, susceptibility, and specific heat data for several of these magnetic compounds. Our group has been studying magnetic ion dynamics, primarily in the Ho/sub x/Lu/sub 1-x/Rh4B4 system, using the muon-spin-relaxation (μSR) technique. Here the authors report low-field measurements for chi=0.02 and chi=0.005, which become superconducting at T/sub c/ approximately equal to 11 K. The results are discussed in terms of a model for the holmium-ion dynamics involving a single-ion conduction electron relaxation mechanism in the presence of strongly perturbing crystalline electric fields