Interactions in γ-Fe₂O₃ and Fe₃O₄ nanoparticle systems

We have investigated interaction effects in two different systems of iron oxide nanoparticles. Samples of γ-Fe₂O₃ and Fe₃O₄ nanoparticles were synthesized using a matrix-mediated precipitation reaction and a chemical co-precipitation technique respectively. The structural properties of these nanoparticles were studied using x-ray diffraction and transmission electron microscopy. We also used temperature dependent ac magnetic susceptibility measurements to carefully investigate the interactions among these nanoparticles. Our analysis showed that the characteristic interaction energy does not depend simply on the average spacing between the nanoparticles but is likely to be strongly influenced by the fluctuations in the nanoparticle distribution