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Ferromagnetism in Ge nanoparticles fabricated by inert gas condensation was investigated. The magnetization was influenced by both the size and the density of Ge nanoparticles. The size was determined by the helium pressure and the density was controlled by depositing Ge nanoparticles on Si substrates at different locations. As the density was increased, the interparticle distance was reduced, which enhanced the magnetic coupling among Ge nanoparticles. The magnetism in Ge nanoparticles was attributed to both the quantum size effect and the magnetic coupling among Ge nanoparticles. By capping a layer over the Ge nanoparticles the magnetization was also enhanced.

Well-isolated FePt(001) nanoparticles embedded in an amorphous SiO2 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.