Magnetic State of Cu in Ferromagnetic Ni

Nuclear magnetic relaxation of ${\mathrm{Cu}}^{63}$ in dilute $\mathrm{Ni}-\mathrm{C}\mathrm{u}$ alloys has been measured in the temperature range 2.1-300 °K. The observed spin echo comes from nuclei in the wings of the domain walls in zero applied field and from nuclei in the saturated bulk in large external field. The longitudinal relaxation rate was found to be proportional to the temperature in both cases. We find $T_{1}T=0.\mathrm{}1$ sec °K and 1.02 ± 0.10 sec °K for zero and high external field, respectively. The difference between these rates is attributed to a mechanism involving the domain walls. Comparison of the high-field rate is made with Moriya's calculation for pure transition metal ferromagnets. It is concluded that there is little or no contribution from the $d$ band to the relaxation of an isolated Cu in Ni. This strongly suggests that a Cu atom in Ni has no local moment.