LATTICE LOCATION AND MAGNETISM OF FE AND SC IMPURITIES IN GD AND TB SINGLE-CRYSTALS

We used the in-beam TD perturbed angular distribution (PAD) technique to investigate the magnetism and lattice location of dilute impurities of Sc and Fe implanted into single-crystal Gd and To host lattices. S c is observed to implant on a unique site, which is almost certainly s ubstitutional. The T=0 hyperfine field B-hf(0) is found to be -5.22(1) T in Gd host and -3.91(3) T in Tb host, both values being corrected f or demagnetizing and Lorentz fields. At higher temperatures, the hyper fine fields deviate from the host lattice magnetization M(B,T); the lo cal susceptibilities however follow Curie-Weiss laws similar to those of the hosts. Fe is found to implant onto two lattice sites, which can be identified by comparison with the similar host Y as substitutional and interstitial sites. The hyperfine fields are small and positive o n both sites, but distinctly larger on the substitutional site. Again, Curie-Weiss behavior is found for the local susceptibilities up to 50 0 K in both hosts. Fe signals are unobservable below T-C, probably owi ng to line broadening.