Magnetic properties of Fe clusters adhering to single-wall carbon nanotubes

Magnetic properties of Fe clusters (diameters: 2-10 nm), encapsulated by thin amorphous carbon layer and adhering to single-wall carbon nanotubes, have been studied. The electron diffraction pattern and magnetic measurement results indicate that the carbon layer encapsulation protects the Fe clusters from surface oxidization. The Fe cluster assembly shows a broad characteristic peak at about TB=260K on the zero-field cooling thermomagnetic curve and has a small coercivity value (∼45 Oe) at room temperature, although the Fe cluster sizes are much smaller than those of a superferromagnetic cluster system without cluster-cluster interactions. These behaviors can be attributed to the large surface anisotropy effects of the small clusters, the wide cluster size distribution and the magnetic interactions between the Fe clusters.