Metal nanogranular films were formed by the high dose (0.25-1.50 x 10¹⁷ ions/cm²) implantation of 40 keV Co⁺ and Fe⁺ ions in polyimide polymer. The implanted samples were annealed at the temperature T= 300 K for 2 hours in vacuum with residual pressure ~10^-6 Torr. Both as-implanted and annealed samples were studied. Transmission electron microscopy investigations showed that the implantation results in formation of metal granules in the irradiated polymer layer with the thickness of about 70 nm. The mean lateral size of metal granules varies from few nm for the cobalt-implanted films up to a hundred nm for the iron-implanted samples, and depends on dose of implantation and post-implanted heat treatment. It was established that annealing procedure promotes coalescence of the granules and increase of their lateral sizes, especially in the cobalt films.

Magnetic resonance studies were performed at X-band (9.5 GHz). No signals were found for as-implanted cobalt samples while Ferromagnetic Resonance (FMR) signal was observed in as-implanted iron films, and in annealed samples (Co and Fe both). The values of the effective magnetization were extracted from the FMR orientation dependence. The FMR absorption intensities were estimated by numerical integration of the spectra. As a result, the plot of the effective magnetization and signal intensity versus implantation dose were obtained for the cobalt and iron films. The magnetic properties of the synthesized composites and their modification due to annealing treatment were discussed. The magnetic parameters of the cobalt and iron implanted granular films were compared.

L.R.T. thanks NIOKR/ANT 06-6.2-47/2002(F) for partial support. R.I.K. acknowledges support by the RBRF, grant No. 00-15-96615.