The results of small-angle ($0.025<Q<\mathrm{}0.125\mathrm{}$ ${\mathrm{\AA }}^{-1\mathrm{}}$) neutron scattering measurements on dilute ferromagnetic $\mathrm{Pd}\mathrm{Fe}$ (0.25, 0.5, 1, and 2 at.%) and $\mathrm{Pd}\mathrm{Mn}$ (0.5 and 2 at.%) alloys are presented. Critical scattering has been clearly observed in a wide temperature interval around the Curie temperature, which for $T>\mathrm{}{T}_C$ could be described by the usual Ornstein-Zernike formalism, but for $T<\mathrm{}{T}_C$ exhibited an extra quasicoherent scattering. Both the temperature and magnetic field dependence of this additional scattering could be explained by the presence of randomly oriented ferromagnetic clusters or microdomains. It is found that a distribution of cluster sizes is necessary to describe the observed scattering. The included magnetic polarization associated with the individual giant moments in $\mathrm{Pd}\mathrm{Fe}$ is obtained from the anisotropic scattering in a magnetic field and gave an average spatial extent of about 50 Å. A comparison of the macroscopic magnetization and the neutron scattering results is made. A modified percolation type of model has been employed to describe the ferromagnetic ordering process, and evidence is provided that the giant moment systems can be characterized as a special case among the more general spin-glass systems.

• Received 24 March 1980

DOI:https://doi.org/10.1103/PhysRevB.22.5426