Controlled Synthesis,Microstructure And Magnetic Properties Of ?-Fe₂O₃/NiO Core/Shell Nanostructures

Bulk NiO is antiferromagnetic,which Neel temperature is 523 K.NiO is also an important semiconductor,with forbidden band width around 4 eV.This makes NiO have important applications in the photovoltaic(pv)and electronic devices,magnetic materials and other industries.During the process of the studying the magnetic properties of NiO nanoparticles,magnetic enhancement,big coercivity,spin glass freeze and unusual hysteresis phenomenon have been found,which is quite different from bulk NiO.Besides,there is interfacial coupling effect in ?-Fe2O3/NiO core/shell nanostructures,thus having an remarkable effect on the magnetic properties such as exchange bias.y-Fe2O3/NiO core/shell nanostructures were prepared by means of pyrolysis synthesis.Through XRD and XPS,we can get the structure ofy-Fe2O3/NiO core/shell nanostructures is fcc and the valence state of Ni is 0 and +2.By SEM,we can observe that most samples are spherical particles(sub)micron in size,which are made up of particles smaller in size.Lattice fringe and interface can be clearly observed by TEM and SAED.The results of SQUID showed the coercivity of y-Fe2O3/NiO core/shell nanostructures at 5 K is up to 276.520e,and the exchange bias is about 28.95 Oe.With the decline of Ni weight fraction,there is rise of coercivity HC and exchange bias HE from 10.43 Oe to 276.52 Oe.