Synthesis and magnetic interaction on concentrated Fe3O4 nanoparticles obtained by the co-precipitation and hydrothermal chemical methods

In this work, a comparative study of the synthesis and magnetic properties of Fe3O4 nanoparticles obtained by the co-precipitation and hydrothermal methods with the adding of the sucrose as a chelating agent is reported. The analysis of transmission electron microscopy (TEM) show that particles are spherical-like with an average particle size ranging of 3 <= d <= 10 nm. Magnetization measurements as a function of an applied magnetic field and temperature are consistent with a superparamagnetic behavior with small T-B values. The analysis of the MvsH loops measured at T = 2 K and Zero-Field-Cooled and Field-Cooled (ZFC - FC) curves allows us to estimate the average diameter of Fe3O4 nanoparticles. These results are in good agreement with those obtained through X-ray diffraction (XRD) data (by using Scherrer equation and Williamson-Hall plot) and slightly smaller than those estimated using TEM images. Finally, ZFC - FC data are also used to evaluate the effective anisotropy constants, which are similar to those values found in literature considering the average sizes values estimated by different techniques.