Interactions between Small Magnetic Clusters in Copper-Rich Cu–Ni–Fe Alloys

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Abstract
Traces of iron in ``nonmagnetic'' Cu‐rich Cu–Ni alloys produce small magnetic clusters largely limited to an Fe site and its Ni nearest neighbors, as observed in Mössbauer source experiments. The present work concerns 57Fe Mössbauer absorber data for higher Fe concentrations (¼%–3%), in the 10%–30% Ni range, which demonstrates the existence of a magnetic‐moment distribution centered about two distinct moment values. For the lower Fe concentrations, the smaller and more abundant of these moments is identical to that observed in the source experiments and is associated with isolated small Fe–Ni clusters. The other moment is about twice as large and can be ascribed to coupled pairs of these small clusters. These results are almost free of effects of metallurgical clustering. By appropriate heat treatment, clustered samples are obtained with different moment distributions and higher Curie temperatures.