Microwave Magnetic Permeability of Fe₃O₄ Nanoparticles

Well-dispersed Fe₃O₄ nanoparticles are synthesized via an oxidization method with NaNO₂ as oxidant. The microwave magnetic properties of the composites are studied with different volume fractions of Fe₃O₄ nanoparticles. It is found that a lower volume fraction corresponds to a higher magnetic resonance frequency. This could be ascribed to the enhancement of exchange interaction with a weakened dipolar interaction when the volume fraction decreases.