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

Abstract

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

Surface effects in the magnetic properties of crystalline 3 nm ferrite nanoparticles chemically synthesized

“…Crystalline 5 nm magnetite nanoparticles were reported in the literature, which shows high magnetization ͑about 60 emu/g͒ and low coercivity field at low temperatures without a considerable contribution of a disordered region. 23 The differences between the nanoparticles of Ref. 23 and our 3 nm nanoparticles consist in the particle size reduction from 5 nm to 3 nm leading to the increment in about 2 times in the surface/volume ratio.…”

“…23 The differences between the nanoparticles of Ref. 23 and our 3 nm nanoparticles consist in the particle size reduction from 5 nm to 3 nm leading to the increment in about 2 times in the surface/volume ratio.…”

“…[20][21][22] Recently, Serna and co-workers 23 showed that the changes in the magnetic properties of ferrite nanoparticles produced by this method with the reduction in the diameter down to 5 nm are continuous as consequence of the high crystallinity degree of the nanoparticles. In addition, the particles synthesized by thermal decomposition are commonly covered by a surfactant ͑e.g., oleic acid͒, and the surface chemical bonding between the organic compound and the magnetite also reduces the relevance of the surface magnetic effects.…”

Reagent control over the composition of mixed metal oxide nanoparticles

“…Furthermore, the d-spacing from high resolution TEM images is within the experimental error of those expected for magnetite (Fe-O) NPs (8.39 A ). [28,29] Given the high thermal stability and low rate of ligand exchange observed for Al(acac) 3 it is unsurprising that there is only minimal incorporation into the Al-Fe-O NPs. If ligand exchange (Equation (1)) is a valid pathway, and the product of such an exchange would be a metal alkoxide, then the use of an alkoxide precursor (with known ability to form the appropriate metal oxide) should enhance the incorporation of the metal into the NPs.…”

Photothermal cancer therapy using graphitic carbon–coated magnetic particles prepared by one-pot synthesis

“…The saturated magnetization value is lower than that of bulk magnetite (92 emu g −1 ) and higher than the values reported for nanoparticles synthesized by decomposition of organometallic complexes. 27 The lower M s values can be attributed to the presence of nonmagnetic carbon components in the samples. The obtained coercivity values are lower than the values for bulk magnetite (200-300 Oe) and comparable with that of magnetite nanoparticles.…”