NEW TECHNIQUE FOR SYNTHESIZING IRON FERRITE MAGNETIC NANOSIZED PARTICLES

Ferrous dodecyl sulfate, Fe(DS)(2), micellar solution was used to make nanosized magnetic particles whose size is controlled by the surfacta nt concentration and by temperature. The average particle size varies from 3.7 to 11.6 nm, with a standard deviation ranging from 0.22 to 0. 34. In contrast to what is obtained in homogeneous solution, iron ferr ite particles can be obtained when the synthesis is performed at very low reactant concentrations and room temperature. Furthermore, nanopar ticles are obtained when the syntheses are performed using Fe(II) as r eactant whereas in homogeneous solution particles in the micrometric r ange are formed. The particle crystallinity varies with the synthesis temperature, going from fairly low values at 25 degrees C to fairly hi gh values at 50 degrees C and above. The particles are characterized b y superparamagnetic behavior. The saturation magnetization decreases w ith particle size, which is explained in terms of non-collinear struct ure at the interface. Particles with low crystallinity are characteriz ed by magnetic diameters smaller than those determined by transmission electron microscopy. This is attributed to crystalline anisotropy.