Hyperfine Field Spectra of Binary Fe-Co Alloys: Nuclear Magnetic Resonance ofFe57andCo59

The distribution of hyperfine fields in iron-rich $\mathrm{Fe}\mathrm{Co}$ binary alloys has been investigated by spin-echo and continuous-wave nuclear-magnetic-resonance techniques. Both the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ and the ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ hyperfine field spectra have been examined. The spin-echo technique is found to give an accurate spectral line shape, without the appearance of extraneous instrumental effects. The anomalously large relative intensity of the prominent satellite line observed in alloys containing a low concentration of cobalt atoms is shown to be the result of a near degeneracy of two distinct resonances; these resonance lines originate at nuclear sites which are nearest neighbors and next nearest neighbors to a cobalt impurity atom. Other lines in the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ spectra which have previously been observed by other workers have been reinterpreted. The distribution of hyperfine fields in this alloy system is believed to result primarily from changes in the core-polarization contribution to the hyperfine field, the changes in the conduction-electron-polarization contribution being substantially smaller.