| 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 geff~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 (geff-factor, linewidth, integrated intensity) was observed. It was found that the temperature dependence of the geff-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. |
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