Nanocrystalline soft magnetic composite materials based on nanocrystalline Ni 3Fe powder ( D=17 nm) and (Ni 3Fe+Fe) mixture have been produced by mechanical alloying. Composite materials have been prepared by covering the nanocrystalline particles with a dielectric polymer binder, then compacted into a toroidal shape and finally polymerized. The frequency dependence of the permeability and losses in the range 1–100 kHz and electrical resistivity were studied in correlation with the dielectric content, tores density and ferromagnetic powder type.