• ferrite nanoparticles;
  • ferromagnetic resonance (FMR);
  • spark plasma sintering (SPS)

Magnetic nanoparticles (NPs) of magnetite and Ni–Zn ferrites, synthesized by the forced hydrolysis in a polyol method, were used as the starting material to consolidate them by means of the spark plasma sintering (SPS) method. The microstructural changes were analyzed by X-ray diffraction, transmission electron microscopy (TEM), magnetic hysteresis loops, and ferromagnetic resonance (FMR) measurements. FMR spectra changed from a high resonance field and small linewidth for the nanoparticles to a spectrum with reduced resonance field with extremely broadened linewidths for the consolidated materials. These effects can be ascribed to the evolution from superparamagnetic NPs to the formation of a nanostructured ceramic structure with high grain-to-grain interactions and with increased randomly distributed anisotropy axes.