Thermal evolution of the ferromagnetic resonance in Fe2O3/SiO2 nanocomposites for magneto-optical sensors

Synthesis and characterization of magnetic mesoporous particles

“…The surface spins would have such an effect on the core, avoiding the possibility of the core spins to rotate. Similar behavior was recently observed in maghemite nanoparticles embedded in a SiO 2 matrix [49].…”

Relationship between nanoparticle growth and magnetic properties of magnetic nanocomposites

“…1(g)). In fact, FMR measurements presented in a previous work [3] showed a paramagnetic signal of Fe 3+ even in a 700°C treated sample. Departing from 180°C, weight loss continues up to 300°C (peaks at 210 and 260°C) due to the carbonization of remaining organic compounds and thermal decomposition of some initial precursors, such as nitrates and formamide [4].…”

“…Within this class of materials, our work is devoted to c-Fe 2 O 3 -SiO 2 NC's with application in magneto-optical sensors. Taking into account the followed preparation method and previously reported results for other particulate systems [2], a superparamagnetic behavior would be expected; however, a predominant blocked state combined with features associated with superparamagnetic NP's is the resulting behavior, as seen in previous Mössbauer, FMR and ZFC/FC measurements [3,4]. The present work is aimed to provide a model of the NP growth and explaining the observed macroscopic magnetic properties.…”

Magneto-optic Faraday effect in maghemite nanoparticles/silica matrix nanocomposites prepared by the Sol–Gel method

“…(1) may arise from the contribution of paramagnetic species, including impurities. It has been found in ferromagnetic resonance experiments [5] that a small amount of iron appears in the form of Fe 3+ ions, embedded in the silica network. Table 1 summarizes the data obtained in the fits of the three magnetization curves to eq.…”