Size-dependent properties of magnetic iron oxide nanocrystals

作者：Demortiere A; Panissod P; Pichon B P; Pourroy G; Guillon D; Donnio B^*; Begin Colin S

来源：Nanoscale, 2011, 3(1): 225-232.

DOI：10.1039/c0nr00521e

The fine control of iron oxide nanocrystal sizes within the nanometre scale (diameters range from 2.5 to 14 nm) allows us to investigate accurately the size-dependence of their structural and magnetic properties. A study of the growth conditions of these nanocrystals obtained by thermal decomposition of an iron oleate precursor in high-boiling point solvents has been carried out. Both the type of solvent used and the ligand/precursor ratio have been systematically varied, and were found to be the key parameters to control the growth process. The lattice parameters of all the nanocrystals deduced from X-ray diffraction measurements are consistent with a structure of the type Fe(3-x)O(4), i.e. intermediate between magnetite and maghemite, which evolves toward the maghemite structure for the smallest sizes (x = 1/3). The evolution of the magnetic behavior with nanoparticle sizes emphasizes clearly the influence of the surface, especially on the saturation magnetization M(s) and the magneto-crystalline anisotropy K. Dipolar interactions and thermal dependence have been also taken into account in the study on the nanoscale size-effect of magnetic properties.

• 出版日期2011