Magnetic-Hyperfine-Structure Coupling and Mössbauer Isomer Shift forAu197in Au-Ni and Cu-Ni-Au Alloys

Mössbauer-effect measurements have been made at 4.2 °K for ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ in the ${\mathrm{Au}}_x{\mathrm{Ni}}_{1-x}$ and ${\mathrm{Cu}}_{x-0.01\mathrm{}}{\mathrm{Ni}}_{1-x}{\mathrm{Au}}_{0.01}$ alloy systems over the full concentration range of noble metal. The effective magnetic field at the ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ nucleus is 272 ± 5 kG for 1-at.% Au in Ni. With increasing concentration of noble metal, this field decreases in direct proportion to the alloy magnetization. For ${\mathrm{Au}}_x{\mathrm{Ni}}_{1-x}$ and ${\mathrm{Cu}}_{x-0.01\mathrm{}}{\mathrm{Ni}}_{1-x}{\mathrm{Au}}_{0.01}$ alloys, the isomer shift is approximately a linear function of composition. These isomer-shift measurements are discussed in terms of a model developed previously to describe the charge-density distribution in concentrated Cu-Au alloys. A good description of the Au isomer shift in the Ni alloys is obtained using the parameters of this model determined previously for the Cu-Au system. The similarity of the electron scattering contribution to the isomer shift by Cu and by Ni is discussed.