Ferromagnetic resonance study of exchange and dipolar interactions in discontinuous multilayers

We studied interlayer and intergranular exchange and dipolar coupling in (Fe97Si3∕SiO2)5 discontinuous multilayer (DM) by means of ferromagnetic resonance (FMR). Due to a strong ferromagnetic exchange coupling (J∼−3ergs∕cm2), the precessional motions of magnetic moments of the granules are coupled, which results in acoustic and optical modes. Moreover, there is a notable FMR line splitting in the optical mode under the external field normal to the DM, which is explained by an interlayer dipolar coupling, only possible for the DMs. The detailed structural analysis and electrical measurements confirmed that the metal nanoparticles were separated by an insulating matrix, and the single-electron transport phenomena (Coulomb blockade and tunneling magnetoresistivity) were observed at low temperatures (77–100K).