Enhancement of the magnetic properties of iron nanoparticles upon incorporation of samarium

Ion implantation of a rare-earth element is shown to dramatically enhance the magnetic properties of Fe nanostructures. Low energy 7 keV Sm+ ion implantation was used to modify the properties of superparamagnetic Fe nanoparticles on the surface of a SiO2 film on Si. The Fe nanoparticles were prepared through low energy ion implantation followed by electron-beam annealing. Ion beam analysis and transmission electron microscopy measurements showed that Sm implantation resulted in the formation of a SmxFe1-xOy layer on top of the Fe nanoparticles and sputtering of Fe in the Fe nanoparticles. There is an enhancement of the saturation magnetization when there is a SmxFe1-xOy layer on top of the Fe nanoparticles. This enhancement is most noticeable for an implanted Sm concentration of 3 × 1015 cm-2 and there is also an enhancement of the susceptibility and hence the permeability by a factor greater than 14. An anomalously large moment per implanted atom is found and which is above the values expected for Fe or any known SmxFe1-xOy compound. High Sm fluences result in complete ablation of the Fe nanoparticles and the magnetic order disappears.