FMR Study of γ-Fe₂O₃ Agglomerated Nanoparticles in Glue

摘要

Three samples containing γ-Fe₂O₃ magnetic nanoparticles (with an average size of about 10 nm) forming agglomerates of different sizes in glue were prepared. Samples 1, 2 and 3 contained agglomerates with average sizes of 1.5 mm, 0.5 mm and 0.2 mm, respectively. At room temperature the position of the ferromagnetic resonance (FMR) line was centered at about g_eff~2 what was essentially different from the position of the FMR line found for small size agglomerates. The temperature dependence of the FMR spectra was carried out in the 90-300K range. Very interesting behavior of the FMR spectral parameters (g_eff-factor, linewidth, integrated intensity) was observed. It was found that the temperature dependence of the g_eff-factor could be described by a simple function c₁+c₂/T, while the linewidth varied with temperature as c₃ exp(-c₄T). The interplay of the dipole and the demagnetization fields, depending on the agglomerate size, determined the values of the FMR spectral parameters as well as their thermal dependence.