Excellent magnetic properties of fullerene encapsulated ferromagnetic nanoclusters

Ferromagnetic nanoclusters are very useful for a magnetic recording. However, application of ferromagnetic nanoclusters is limited due to air-oxidation. One way to solve air-oxidation is to encapsulate ferromagnetic nanoclusters with inert materials such as carbon when they are produced. This allows us to keep excellent magnetic properties for a long time. In this work, we report a very simple synthetic method of fullerene (i.e., onions and nanotubes) encapsulated ferromagnetic nickel and cobalt nanoclusters by thermally decomposing metallocene vapors with a resistive heater. Protection from air-oxidation was tested by annealing encapsulated ferromagnetic nanoclusters in air up to ∼ 180°C for half a day and then, recording XRD patterns. No oxide peaks were observed in the XRD patterns, indicating that oxidation protection via fullerene encapsulation is very good. Magnetic property measurement showed that both fullerene encapsulated nickel and cobalt nanoclusters possessed excellent magnetic properties.