We show that the appearance of a localized moment on Ni atoms in the critical range of concentration is accurately described by a simple environment-dependent model of the Jaccarino-Walker type, and that this model implies a "clustering" of magnetic moments, even on the basis of a random distribution of atoms. The fit with experimental data is promising in view of the approximations made.

• Received 24 November 1969

DOI:https://doi.org/10.1103/PhysRevLett.24.313