Ferromagnetic resonance in Ni–Zn ferrite nanoparticles in different aggregation states

Abstract

Ferrite nanoparticles of composition Zn0.5Ni0.5Fe2O4 were synthesized by forced hydrolysis in polyol from the corresponding zinc, nickel and iron acetates. By varying the preparation conditions, different aggregation states were obtained, ranging from isolated nanoparticles with average diameter of 5nm, to clusters of some 20nm, formed as well by nanoparticles with average diameter in the 5nm range, as confirmed by X-ray diffraction and high resolution transmission electron microscopy. Ferromagnetic resonance measurements exhibited a ferrimagnetic behavior for both aggregation states at 77K; at 300K, however, isolated nanoparticles showed a superparamagnetic behavior while clustered ones remained ferrimagnetic with a broad linewidth. These results are interpreted on the basis of interactions between nanoparticles.