WEDNESDAY 14:00
MAGNETIC COUPLING OF CEMENTITE NANOPARTICLES WITHIN DOUBLE-WALL CARBON NANOTUBES
Dario Niebieskikwiat
Universidad San Francisco de Quito, Ecuador
ABSTRACT
Studying the novelty of magnetism of p-electron systems in carbon-nanotube related nanostructures is still intriguing and have not been completely explored, in spite of the possibilities for technological applications. In this study, we have focused on the magnetic properties of bundles of double-walled, metallic carbon nanotubes with encapsulated cementite (Fe3C) nanoparticles of around 3 nm in length inside the hollow core. These nanoparticles are not unintentional impurities, but have been deliberately introduced to fill the nanotubes with a ferromagnetic material. A systematic analysis of the magnetic properties of the nanotubes gives an anisotropy constant of around 3 x 106 erg/cm3, much larger than the anisotropy of free cementite nanoparticles, thus indicating a strong magnetic coupling of the nanoparticles with the nanotubes. On the other hand, the calculated activation volume for magnetization reversal, of ~ 400 nm3, indicates that around 300 nanoparticles of cementite are mutually coupled through the conduction electrons of the nanotubes. Considering a spin diffusion length of around 130 nm along the direction of the nanotubes, the activation volume suggests that a magnetic coupling also occurs between neighbouring nanotubes in the direction perpendicular to their axis, with a perpendicular magnetic correlation length of around 5 nm which involves around four parallel nanotubes.