Lattice location and magnetism of Fe and Sc impurities in Gd and Tb single crystals

Abstract 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 Tb host lattices. Sc is observed to implant on a unique site, which is almost certainly substitutional. 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 for demagnetizing and Lorentz fields. At higher temperatures, the hyperfine fields deviate from the host lattice magnetization M(B,T) ; the local 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 on both sites, but distinctly larger on the substitutional site. Again, Curie-Weiss behavior is found for the local susceptibilities up to 500 K in both hosts. Fe signals are unobservable below T C , probably owing to line broadening.