FMR Study of Temperature Dependence of Magnetic Properties of Nanocrystalline $0.90(Fe_2O_3)$/0.10ZnO

The nanocrystalline mixed system $0.90(Fe_2O_3)$/-0.10ZnO has been prepared by coprecipitation and calcination processes. The phase composition of samples was determined by X-ray diffraction. The studied nanocrystalline sample is dominated by phase $Fe_2O_3$ but very small amounts of ZnO and $ZnFe_2O_4$ phases were also identified. The ferromagnetic resonance investigations of the obtained sample have been carried out in the temperature range from liquid helium to room temperature. The asymmetrical and very intense magnetic resonance line was recorded at all temperatures. A significant shift of spectra towards lower magnetic fields with decreasing temperature was observed. A very good fitting by two Lorentzian functions has been obtained which suggested the existence of a strong anisotropic magnetic interaction. Some similarities in behaviour of ferromagnetic resonance parameters of the present sample and the $0.95Fe_2O_3Fe2O3$/0.05ZnO sample were noticed but the parameters values were essentially different. The gradients Δ $H_{r}$/Δ T (where $H_{r}$ is the resonance field), the broadening processes of the resonance lines as well as the line amplitudes were changing more intensely changing with temperature in comparison to sample $0.95Fe_2O_3Fe2O3$/0.05ZnO. The following values Δ $H_{r}$/Δ T are obtained: 16.7(1) Gs/K and 20.7(1) Gs/K over the 60 K temperatures where below 40 K is 41.5(1) Gs/K and 56.0(1) Gs/K. The reorientation processes were more active at low temperatures for smaller concentrations of magnetic nanoparticles