Synthesis and exchange bias effect of CoFe2O4/CoO composite ceramics

Composite ceramics composed of the ferrimagnetic (FM) CoFe2O4 and the antiferromagnetic (AFM) CoO were synthesized by using the chemical combustion method. The characterization measurements including X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis show that CoFe2O4 nano-particles are embedded in CoO matrix. The magnetic measurements show that the hysteresis loops display a small negative exchange bias field (He) of 106 Oe as the ceramic is cooled to 10 K in an applied field of 10,000 Oe. Furthermore, the magnetic parameters including coercivity, remanence, and He show clear dependence on temperature and the applied magnetic field in the cooling procedures. This exchange bias effect is ascribed to the exchange coupling at the FM/AFM interfaces.