Structural and magnetic properties of multiwall carbon nanotube arrays with incorporated iron-phase nanoparticles

We have performed an experimental study of the structure, composition and magnetic properties of carbon nanotube (CNT) arrays at different catalyst source concentrations during their synthesis. Floating catalyst chemical vapor deposition was chosen for the synthesis of CNT arrays as a low-cost, simple and effective technique. Various concentrations of ferrocene/xylene solution used as a feedstock for CNT growth allowed obtaining arrays of aligned multi-wall CNTs on Si/SiO2 substrates with different percentage content, shape and aspect ratio of catalyst inclusions being incorporated in the channels and between the shells of CNTs. In this way the nanoparticles are mostly isolated from interaction with each other, and protected from oxidation in the air atmosphere. The structure and composition of the obtained material was investigated by scanning and transmission electron microscpies, Raman, Mцssbauer spectroscopies, and X-ray diffraction. Magnetic properties of CNT arrays were studied by SQUID magnetometer in parallel and perpendicular to the substrate directions at various temperatures (2-380 K). Our results show that magnetic properties of CNT- iron phases can be easily varied depending only on the initially used catalyst source concentration for CNTs synthesis