X-ray diffraction pattern for Fe3O4 nanoparticles with 〈D〉 = 40 nm.
Fe3O4 nanoparticles in-phase susceptibility curves for temperature ranging from 5 to 150 K. At the inset, out-phase susceptibility curves; the peak shifting with frequency is pointed.
Activation energy, Ea, dependence on frequency. The inset shows the in-phase susceptibility curves with their corresponding fittings.
Hysteresis loops for Fe3O4 nanoparticles at different temperatures. At the inset, a zoom to the coercivity values, where a big decrease on coercivity confirmed the spin-glass transition.
Activation energy, Ea, and relaxation time, τ, calculated from magnetic susceptibility curves for the different frequencies.
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