Features of FMR spectra observed in granular films formed by Fe+ implantation into PMMA

Magnetic phase consisting of α-Fe particles arranged in a thin near-surface layer has been synthesized in modified phosphorus-containing polymethylmethacrylate by Fe⁺ implantation at an energy of 40 keV with a dose of 1.2⊙10¹⁷ ion/cm². The spectrum of magnetic resonance of the obtained samples is a superposition of a wide anisotropic absorption line and a set of reproducible lowintensity noiselike signals registered in a wide range of magnetic field. It has been established that a wide absorption line is due to particle conglomerates (larger than 200 nm), each behaving as a thin ferromagnetic film. Noiselike lines can be explained as resonance signals from separate oblate/prolate nanoparticles (50–200 nm in size) randomly oriented with respect to the irradiated surface. Such complicated nanostructures can be formed at an appropriate combination of properties of a polymer matrix, types of bombarded ions and implantation regimes.