Ordered NiO/NiFe2O4 nanocomposites: Synthesis, exchange bias and magnetic properties

Abstract

Mesoporous bundled NiFe2O4 nanowires were synthesized using mesoporous silica SBA-15 as hard template, and then NiO nanoparticles were implanted into NiFe2O4 nanowires to prepare ordered NiO/NiFe2O4 nanocomposites. X-ray diffraction, N2 adsorption-desorption, transmission electron microscopy and energy dispersive spectrometer were used to characterize the microstructure of the as-prepared samples. All results indicated that mesoporous NiFe2O4 nanowires presented in bundle with the pore-volume percent of about 42% and NiO nanoparticles existed in the mesopores. The magnetic behavior of NiFe2O4 nanowires and NiO/NiFe2O4 nanocomposites were investigated with superconducting quantum interference device, and the saturation magnetization decreased with the increasing NiO content, while the coercivity and exchange bias field increased. The exchange bias effect was obviously observed for the NiO/NiFe2O4 nanocomposites at low temperature and increased with the NiO content. It's concluded that interfaces magnetic interactions and surface energy barrier of NiO nanoparticles greatly affected the magnetic behavior of the NiO/NiFe2O4 nanocomposites.