LAUSR

Abstract Low energy implantation of Ni and Fe into SiO2 films resulted in the formation of superparamagnetic Ni1-xFex nanoparticles for Ni fluences of 2 × 1016 at./cm2, 4 × 1016 at./cm2, and 6 × 1016 at./cm2 where the Ni:Fe fluence ratios were 47:56, 53:47, and 63:37, respectively. Small ∼5 nm Ni1-xFex nanoparticles were dispersed in the implantation region for the lowest Ni fluence. Increasing the Ni fluence resulted in a different nanoparticle morphology where larger nanoparticles appeared at the surface and small Ni1-xFex segregated regions to a depth of ∼20 nm. The average nanoparticle size in the surface region was ∼8 nm for Ni fluences of 4 × 1016 at./cm2 and 6 × 1016 at./cm2. The highest Ni fluence film also had smaller Ni1-xFex nanoparticles at a depth of ∼11 nm. The largest high field moment per implanted ion was found for the intermediate Ni fluence. The spin-stiffness was similar for all fluences and smaller than that expected for bulk Ni1-xFex. A small spin-disordered region was evident with the same low spin-freezing temperatures that may be due to a similar spin-disordered shells. dM/dH at 300 K was estimated and found to be highest for a Ni fluence of 4 × 1016 at./cm2 where it reached 62.