Structural and magnetic properties of uniform magnetite nanoparticles prepared by hightemperature decomposition of organic precursors

Abstract

Magnetite nanoparticles (Fe3O4) of three different sizes below the limit for single domain magnetic behaviour have beenobtained by thermal decomposition of an iron precursor in an organic medium in thepresence of a surfactant. Good agreement between mean particle size obtained by TEM,crystal size calculated from x-ray diffraction and magnetic diameter calculated frommagnetization curves measured at room temperature shows that the samples consist ofuniform, crystalline and isolated magnetite nanoparticles with sizes between 5 and 11 nm.High saturation magnetization and high initial susceptibility values have been found, thelatter decreasing as the particle size decreases. The main contribution to the anisotropy ismagnetocrystalline and shape anisotropy, since surface anisotropy is suppressed by theoleic acid molecules which are covalently bonded to the nanoparticle surface.