Anomalous transferred hyperfine interactions in bulk and epitaxial Tb:Y alloys: a NMR study

Abstract

We have made an NMR study of the effect of yttrium substitution on the hyperfine splitting of in ferromagnetic terbium at 4.2 K. In conventionally prepared polycrystalline samples the average transferred hyperfine field increases linearly with yttrium content, an effect attributed to the reduction of the negative transferred hyperfine fields from the 4f spins on neighbouring Tb ions. The rate of increase, however, is about half of that expected from similar measurements on inter-rare-earth alloys. We have also studied the transferred hyperfine interaction in epitaxially grown laminae of Tb containing 5% and 10% Y, in which resolved satellites associated with individual nearest-neighbour Y atoms are observed. The satellite shift, per unit change in 4f spin, 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 simple spin diluent, and that it makes a substantial contribution to the transferred hyperfine field.

Interdiffusion in a superlattice: an exploratory nuclear magnetic resonance study

“…The three-line quadrupole-split NMR spectra obtained from the superlattice are characteristic of 159 Tb and are qualitatively similar to those previously obtained for epitaxially grown Tb:Y alloys (Li et al 1996). The spectra taken in finite fields are shifted upwards in frequency by ∼ =10 MHz T −1 , which corresponds closely to the gyromagnetic ratio of 159 Tb.…”

“…The central line is shown in figure 4, together with the corresponding line for a Tb 0.95 Y 0.05 alloy. Li et al (1996) have shown that transferred hyperfine interactions in Tb:Y alloys are dominated by isotropic contributions from the 12 nearest neighbours. The satellite structure shown in figure 4(a) arises from Tb ions with n = 0, 1, 2 and 3 Y ions in the nearestneighbour shell.…”

“…The work to be described is an exploratory NMR study of interdiffusion between terbium and yttrium at the interfaces in a Tb|Y superlattice grown by MBE. It draws on results obtained in our recent study of transferred hyperfine interactions in epitaxial Tb:Y alloys (Li et al 1996). For the reasons outlined in the preceding paragraph, we include a substantial discussion of the nature of the diffusion profile as well as its relationship to the NMR spectrum.…”