Magnetization Reversal Mechanism and Microstructure Refinement of the FePt (001) Nanogranular Films With SiO $_{2}$ Capping Layer

Ordered FePt continuous thin films with an amorphous SiO₂ single capping layer have been fabricated on MgO (001) single-crystal substrates by the electron beam deposition technique at 400degC in order to investigate the effects of SiO₂ capping layer on microstructure and magnetic reversal process of the FePt (001) thin films. The formation of nanogranular-like FePt films was directly obtained with this process due to the interpenetration of SiO₂ which has a lower surface energy than that of pure Fe or Pt. Studies of angular dependent coercivity show a tendency of a domain-wall motion weaken towards rotation of reverse-domain type upon thickness of SiO₂ capping layer on the FePt thin films. The intergrain interaction was confirmed from the Kelly-Henkel (deltaM) plot that indicated the strong exchange coupling between neighboring grains in the FePt continuous films without SiO₂ capping layer. On the other hand, negative deltaM value was obtained when the FePt films with SiO₂ capping layer, indicating the SiO₂ capping layer, can lead to the reduction of intergrain exchange coupling thus presence of dipole interaction in the SiO₂/FePt nanocomposite thin film structures.