Electron holography of single-crystal iron nanorods encapsulated in carbon nanotubes

alpha-Fe nanorods encapsulated in multiwall carbon nanotubes (CNTs) were characterized by x-ray diffraction (XRD), high resolution electron microscopy (HREM), and electron holography. HREM observations revealed that the alpha-Fe nanoparticles were single crystals with a preferential growth direction of < 200 >(alpha-Fe) oriented along CNTs. Phase distributions of an alpha-Fe nanorod were measured by electron holography and the remanent state was retrieved by a three-dimensional morphological model and an algorithm with the consideration of irregular nanoparticle shape. It was found that the saturated magnetization of the alpha-Fe nanorod with a CNT outer shell was very close to that of bulk pure alpha-Fe, suggesting that the core-shell nanostructure effectively prevented the surface oxidation that had been found to significantly degrade the magnetic properties of nanostructured alpha-Fe. (c) 2007 American Institute of Physics.