Nano-clustering in α-Al2O3 crystals by ion implantation of iron and cobalt and their magnetic properties

Nano-composites of iron-based alloys in α-Al2O3 matrices were formed by sequential implantation of Fe and Co ions. The implantation was done at room temperature up to a total dose of 2.0×1017 ions/cm2 with a projectile energy of 100 keV. We have observed an apparent change in magnetic properties of Fe–Co clusters with 0–60 at.% Co contents, which gives evidence of Fe–Co alloying. Mössbauer spectroscopy shows that hyperfine field at 57Fe nuclei changes with Co substitution of 57Fe in the nano-sized binary clusters while the blocking of superparamagnetic relaxation occurs when the Co concentration increases in the alloy clusters. The results are in good agreement with magnetization measurements.