Magnetic properties of Fe3C ferromagnetic nanoparticles encapsulated in carbon nanotubes

The low-temperature dependences of magnetic characteristics (namely, the coercive force Hc, the remanent magnetization Mr, local magnetic anisotropy fields Ha, and the saturation magnetization Ms) determined from the irreversible and reversible parts of the magnetization curves for Fe3C ferromagnetic nanoparticles encapsulated in carbon nanotubes are investigated experimentally. The behavior of the temperature dependences of the coercive force Hc(T) and the remanent magnetization Mr(T) indicates a single-domain structure of the particles under study and makes it possible to estimate their blocking temperature TB = 420–450 K. It is found that the saturation magnetization Ms and the local magnetic anisotropy field Ha vary with temperature as ∼T5/2.