Exchange bias and enhanced anisotropy from exchange coupled Fe3C/CoO nanoaggregates

A comparative magnetic study was conducted on Fe3C and Fe3C/CoO for potential enhancement in magnetic properties due to exchange interaction in ferro/antiferromagnetic systems. X-ray diffraction confirmed the presence of iron carbide and CoO while XPS determined presence of a CoFe2O4 and a small percent of FexCoxC at the interface. Transmission electron microscopy showed a polydispersed network of 47 nm of Fe3C coated with 17 nm CoO nanoparticles. Due to the intrinsic nature of the interface an enhanced coercivity (600 Oe) above the blocking temperature was observed in comparison to the bare Fe3C nanoparticles (450 Oe). Upon cooling below the Néel temperature and Verwey temperature for CoO and CoFe2O4 a maximum exchange bias of 150 Oe occurred at 50 K. Results have shown a plausible way to enhance the anisotropy of the iron carbide while broadening its potential applications for spin valve systems.