Nuclear Resonance in Ferromagnetic Alloys

Abstract

The internal fields Hi in ferromagnetic alloys were measured at both the solvent and the solute nuclei at magnetic and nonmagnetic atoms using NMR techniques. Co59 resonances in Co-rich alloys (Co-Fe, -Ni, -Cu, -Cr, -Mn, -Al) have fine structures which depend on the kind and the concentration of impurity metals. Similar structures are found for the Fe57 resonances in Fe-rich alloys. These structures are tentatively interpreted as caused by the anisotropy of Hi at the nearest neighbors. The Co59 resonance is also observed in Fe-rich Co-Fe alloys, and it is found that Hi seen at the Co site is lower by about 50 koe than that at the Fe site. The Co59 line width is about 400 kc for (Fe+1% Co) alloy. Both the temperature and the pressure dependences of the Co59 frequency were measured. Hi at Cu63 and Cu65 was measured in Co-rich Co-Cu and in Fe-rich Fe-Cu ferromagnetic alloys. The magnitude of these internal fields at Cu and their observed pressure dependence are, at least, not inconsistent with the contention that the observed Hi is mainly produced by the 4s conduction-electron polarization, although Hi at the Cu nucleus, 217.7 koe for Fe-Cu alloy and 157.5 koe for Co-Cu alloy, is considerably higher than the usual theoretical prediction.