Fe57Mössbauer Effect in Cu-Ni Alloys

The Mössbauer effect of ${\mathrm{Fe}}^{57}$ has been used to study the properties of iron impurity atoms in the complete range of composition of Cu-Ni alloys. The isomer shift indicates a small decrease in the total electronic density at the ${\mathrm{Fe}}^{57}$ nucleus in going from pure Ni to pure Cu. The magnetic field at the iron nucleus at 0°K decreases by 9% in the range from 0 to 40% Cu. Both results show that only minor changes take place in the atomic configuration of the iron. The linewidth, measured in the paramagnetic alloys, is smallest in pure copper and largest near the middle of the composition range. The rapid change in linewidth with small nickel admixture can result from quadrupole splitting due to the field gradients arising from the spatial charge fluctuations around an impurity atom. Some of the broadening can also arise from an inhomogeneous isomer shift due to a range of surroundings of an iron atom in the alloy.