Unsaturated Modes of Ferromagnetic Resonance in Maghemite Nanoparticles

In this study, we present an investigation of Ferromagnetic Resonance (FMR) at various microwave frequencies (1.1 GHz, 3.5 GHz, 9.4 GHz, and 33.9 GHz) for maghemite
$(\boldsymbol{\gamma}-\mathbf{Fe}_{\mathbf{2}}\mathbf{O}_{\mathbf{3}})$
nanoparticle samples in both powder and aqueous ferrofluid forms. Their structure was confirmed through X-ray Diffraction (XRD), revealing an average diameter of 12.1 nm. Analysis of the FMR spectra obtained at room temperature (RT) suggests that the samples are in a non-saturated state for microwave frequencies below 10 GHz.