Magnetic carbon nanotube (CNT) composites have been successfully fabricated by employing a one-step approach, in which ferrocene decomposed at high temperatures of 350 °C, 425 °C, 500 °C, and transformed into iron oxides to deposit on CNTs. The resulting products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy (TEM). It was found that CNT–maghemite composites sheathed with amorphous carbon-based material were achieved at 500 °C. TEM observation indicated that the produced maghemite particles not only decorated the external walls of CNTs but also were encapsulated within CNTs. The magnetic phase, size and amount of magnetic nanoparticles deposited on the CNTs could be controlled by varying the processing temperature. Magnetic measurements demonstrated that the composites prepared at 500 °C were ferromagnetic, while the composites obtained at 350 °C and 425 °C became superparamagnetic and showed no remanence or coercivity.
