/sup 11/B study of spin dynamics in Y/sub 1-x/RE/sub x/Rh/sub 4/B/sub 4/. [RE = Gd, Er]

There has been intense interest in re-entrance and coexistence in ternary rare earth magnetic superconductors of the form RE Rh/sub 4/B/sub 4/. Of particular interest in this investigation is the effect of the superconducting state on the RKKY (Yosida, 1957) coupling between RE ions. Since one expects the conduction electron spin susceptibility chi/sup e/(q) to be cut off for q < 1/xi in the superconducting state, a depression f the RKKY coupling should follow. Such an effect would both depress the magnetic ordering temperature and result in slower relaxation rates tau/sub m//sup -1/ for the RE moments in the superconducting state. This paper reports on the spin dynamics of the RE ions using the /sup 11/B nuclear magnetic relaxation rate T/sub 1//sup -1/ in dilute Y/sub 1-x/RE/sub x/Rh/sub 4/B/sub 4/ (RE = Gd and Er).