Magnetic Clusters Associated with Isolated Fe Atoms in Paramagnetic Cu-Ni Alloys

A small magnetic cluster is shown to exist around an isolated Fe atom in ${\mathrm{Cu}}_{1-X}{\mathrm{Ni}}_X$ alloys with a magnetic moment and saturation hyperfine field depending on the number $n$ of Ni near neighbors. This small cluster changes abruptly from moments of $\mathrm{}(2.85+0.6n)\mathrm{}\times {\mu }_{\mathrm{B}}$ to large moments [$\left(\sim 17 \mathrm{to} 20\right){\mu }_{\mathrm{B}}$] for Ni concentrations near the critical composition. The moment compensation (Kondo effect) found for isolated Fe in Cu appears to persist in Cu-Ni up to at least 10 at.% Ni.