Exchange interaction at the interface of Fe–NiOnanocomposites

Fe–NiO nanocomposites with Fe to NiO ratio 20:80, 30:70 and 50:50 were prepared by a chemical route. X-ray diffraction and TEM measurements showed the presence of α-Fe and NiO phases in the prepared nanocomposites having an average crystallite size 17 nm. HRTEM image showed a structurally disordered phase at the Fe–NiO interface. Mössbauer spectra of the nanocomposites consist of a doublet along with a sextet corresponding to relaxed and blocked α-Fe phases, respectively. The dc magnetization measurements in field-cooled condition show a shift of hysteresis loop and an enhancement of coercive field at low temperature confirming the presence of exchange bias at Fe–NiO interfaces. The irreversibility observed in the FC and ZFC magnetization measurements also points to exchange bias effect.