Self-organized magnetic assemblies of (001) oriented FePt nanoparticles with SiO₂ additive

Well-isolated FePt(001) nanoparticles embedded in an amorphous SiO ₂ matrix have been successfully fabricated via a molecular-beam epitaxy technique on MgO(001) single-crystal substrates via the introduction of a SiO₂ intermediate layer into the FePt film structures, the critical thickness of which is 10 nm. The formation of two-dimensional magnetic assemblies of ordered FePt(001) nanoparticles with an average size of about 6 nm was directly obtained with this process at only 400°C due to the interpenetration of SiO₂ which has a lower surface energy. Studies of angular-dependent coercivity show a tendency of a domain-wall motion shift towards rotation of reverse-domain type upon insertion of the SiO₂ into the FePt structures, and domain rotation is enhanced, leading to a decoupling of intergrain interaction, as identified with δM measurement.