Carbon nanotubes; Giant magnetoresistance; Magnetic nanowires Anisotropy; Carbon nanotubes; Coercive force; Encapsulation; Giant magnetoresistance; Iron; Magnetic properties; Magnetization; Scanning electron microscopy; SQUIDs; Transport properties; X ray diffraction analysis; Magnetic nanowires; Nanowires; Temperature dependence; Ultrahigh density storage; Nanostructured materials