Nuclear-Resonance Spin-Echo Study ofNi61Hyperfine Fields in Ferromagnetic Ni-Al, Ni-V, and Ni-Cr Systems

Abstract

The nuclear-magnetic-resonance line shapes of ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}$ have been studied in ferromagnetic Ni-rich Ni-Al, Ni-V, and Ni-Cr powders by plotting the spin-echo amplitude as a function of frequency across the inhomogeneously broadened resonance lines. The measurements were made at 4.2°K in alloys containing concentrations of up to 12.3 at.% Al, 5.5% V, and 5.3% Cr. In all three systems, the average hyperfine fields decreased approximately linearly with increasing solute concentration. A general discussion of the relationship between the average hyperfine field and the atomic moments is presented. The major contribution to the hyperfine field is believed due to the moment on the parent atom, with a smaller contribution from moments on neighboring atoms via conduction-electron polarization. The detailed structure of the resonance spectra is analyzed. It is found that the magnetic disturbances are spatially more widespread in the Ni-Al and, Ni-V systems than in the Ni-Cr system. The Ni-Cr system in turn has a more delocalized behavior than the Ni-Co system previously studied. The results in the Ni-V and Ni-Cr systems are consistent with results obtained by Collins and Low using neutron scattering techniques.