Anisotropic Hyperfine Interactions in ZrFe2 and GdFe2 from a Nuclear Magnetic Resonance Study

Abstract

We have studied the nuclear magnetic resonance of ⁵⁷Fe nuclei in the magnetic state of both ZrFe₂ and GdFe₂, using the technique of spin echoes. The broad spectrum from the iron nuclei in ZrFe₂ at 4.2°K could be resolved into one weak and one strong line located at 28.9±0.2 Mc/sec and 30.6±0.1 Mc/sec, respectively. The frequencies of these lines are in good agreement with the Mössbauer results in this system which show two lines, with an intensity ratio of 3 to 1, arising from nuclei in domains. The application of magnetic fields less than 4π/3 M_s to the stronger Zr resonance at 77°K produces a detectable frequency shift and a decrease in intensity of the spin‐echo signal. In GdFe₂, a ferrimagnet, a similar spin‐echo spectrum for the iron is observed with one weak and one strong line at 31.3±0.3 Mc/sec and 32.4±0.1 Mc/sec, respectively. The difference between this system and ZrFe₂ may be understood in terms of the contribution from the magnetic gadolinium sublattice. We conclude that in these systems, the anisotropy observed by the Mössbauer technique is detectable in nuclear spin‐echo spectra.