Synthesis and magnetic properties of core–shell nanoparticles under hydrothermal conditions

γ-Fe2O3/SiO2 core–shell nanoparticles with an average diameter by about 30 nm were synthesized by hydrothermal reaction of Tetraethoxysilane and Fe(NO3)3⋅9H2O as precursors. The phase component, structure and magnetic properties of the nanoparticles were characterized by X-ray diffraction, transmission electron microscopy and magnetic measurements. The results show that the uniform γ-Fe2O3 nanoparticles were capped with an amorphous SiO2 thin shell by about 5 nm in the thickness. The effect of hydrothermal temperature and growth mechanism were discussed towards the end of this paper. The magnetic property of nanoparticles was also discussed.