FMR study of γ-Fe2O3 agglomerated nanoparticles dispersed in glues

Four samples of gamma-Fe2O3 magnetic nanoparticles (size 10 nm) in an agglomerates state (size 100 mu m) dispersed in different glues TEC 418511 modified acrylic (sample 1), TEC 4185 acrylic (sample 2), Durotak 280-122A acrylic PSA (sample 3), and Aroset 8084 acrylic PSA (sample 4), have been investigated by ferromagnetic resonance (FMR) method at room temperature. To study the influence of agglomerate size on the FMR spectrum, two additional samples have been prepared with aggregates of 2 mm and 100 nm in diameter. Very intense and broad FMR Lorentzian lines have been recorded for all six studied samples. The values of the resonance lines are quite similar for all samples, they were characterized by g(eff)=2, indicating that the internal magnetic field is almost zero. This is in contrast with agglomerates embedded in harder matrices, for which a larger shift had been observed.