(Color online) Schematic representation of the unit cell of maghemite.
(Color online) (a) Schematic representation of the silica coating steps. (b) TEM images (from Ref. 12) and schematic representation of the γ-Fe2O3 nanoparticles before and after the silica coatings.
(Color online) Mössbauer spectra of (a) uncoated γ-Fe2O3 MNPs measured at RT and (b) γ-Fe2O3@SiO2−2 MNPs (silica shell thickness of ∼110 nm) measured at RT.
(Color online) (a) Mössbauer spectrum of uncoated γ-Fe2O3 MNPs measured at 77 K. (b) Hyperfine field distribution.
(Color online) (a) Temperature dependence of the normalized magnetization [M/M FC (5K)] for ZFC and FC curves. (b) Reciprocal susceptibility curves (normalized ZFC).
(Color online) Magnetization vs applied magnetic field of γ-Fe2O3 nanoparticles at 5 K. Inset: scheme of the dead layer in the external surface of the MNPs.
Selected Mössbauer parameters at 300 K for 6.5 nm γ-Fe2O3 nanoparticles uncoated and coated with silica. δ is the isomer shift with respect to metallic iron at RT, Δ is the quadrupolar shift, Γ is the linewidth (full-width at half maximum), B hf is the hyperfine field, and Area is the area below the spectrum.
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