ANOMALOUS TRANSFERRED HYPERFINE INTERACTIONS IN BULK AND EPITAXIAL TB-Y ALLOYS - A TB-159 NMR-STUDY

We have made an NMR study of the effect of yttrium substitution on the hyperfine splitting of Tb-159 in ferromagnetic terbium at 4.2 K. In c onventionally prepared polycrystalline samples the average transferred hyperfine field increases linearly with yttrium content, an effect at tributed to the reduction of the negative transferred hyperfine fields from the 4f spins on neighbouring Tb ions. The rate of increase, howe ver, is about half of that expected from similar measurements on inter -rare-earth alloys. We have also studied the transferred hyperfine int eraction in epitaxially grown laminae of Tb containing 5% and 10% Y, i n which resolved satellites associated with individual nearest-neighbo ur Y atoms are observed. The satellite shift, per unit change in 4f sp in, is less than half of that observed in epitaxially grown Ho:Dy and Ho:Gd alloys. We conclude that the nominally non-magnetic Y is not a s imple spin diluent, and that it makes a substantial contribution to th e transferred hyperfine held.