Temperature and field independence of the fluorine and lithium NMR shift tensors in lithium rare-earth tetrafluorides
The fluorine and lithium NMR line shifts have been followed in temperature from 300 to 1.3 K and in fields up to 40 kG for LiTbF4 and LiHoF4. The Tb3+ and Ho3+ ionic moments cause these shifts. The Li shifts are dominated by dipole interactions, whereas the F shifts also have transferred hyperfine contributions of comparable sizes. The transferred hyperfine interactions turn out to be almost isotropic and exhibiting no temperature or field dependence. In LiHoF4 the line shifts are detectable within the entire temperature range. In LiTbF4 the fluorine and lithium lines broaden to such an extent that they disappear in a region from 10 to 60 K and from 15 to 40 K, respectively, probably due to a long relaxation time of the Tb ionic moment.