The change from paramagnetic resonance to ferromagnetic resonance for iron nanoparticles made by the sol–gel method

Abstract

Sol–gel glass embedded with iron nanoparticles provides fascinating features inheriting paramagnetic, ferromagnetic, and superparamagnetic resonance properties under various compositional weight ratios and annealing conditions. Two spectra arising from paramagnetic Fe 3+ ions and ferrimagnetic Fe 2O 3 particles both centered at g e=2.0 compete with intensities as the annealing temperature T A increases. Meanwhile, the resonance line width of Fe 2O 3 particles sharply decreases due to the strong exchange narrowing. The asymmetric line shape and the rather broad line width can be elucidated by the ferromagnetic resonance of the single domain Fe 2O 3 nanoparticles.