Size (dHRTEM) distribution of ε-Fe2O3 particles in sample 05FS (0.74% ε-Fe2O3/SiO2) obtained from the HRTEM data and effective size (deff = dHRTEM–2 × 0.31 nm) distribution with regard to “paramagnetic” surface Fe(III) atoms for dHRTEM < 3.5 nm (shown by the vertical dashed line). Schematic of the model for the particles with dHRTEM < 3.5 nm and dHRTEM > 3.5 nm.
Mössbauer spectra of the samples with (a) 0.74% (05FS) and (b)3.4% Fe (3FS) annealed at different temperatures.
Experimental temperature dependences M(H = 60 kOe) (dark symbols) for the investigated sample and SP contribution at H = 60 kOe (lightsymbols) after subtraction of the paramagnetic contribution 65 emu/g× B(H, T) (dashed curve). Temperature dependences of the magnetic moment M(T) in the ZFC and FC regimes. Inset: M(T) in the fields H = 1 (ZFC and FC) and 10 kOe (symbols) and corresponding SP contributions (solid curves). The arrow shows the blocking temperature at H = 1 kOe.
Field dependence of the magnetic moment M(H) at T = 4.2 K for the studied sample (circles) and corresponding SP contribution (triangles) after subtraction of the paramagnetic contribution 65 emu/g × B(H, T) (dashed curve). Inset: M(H) hysteresis of the SP contribution in the low-field range.
The experimental M(H) dependences (symbols) of studied sample at different temperatures (given in the figure) and results of the best fit by Eq. (1) (red solid curves). Also shown the SP and paramagnetic contributions (black solid and dashed curves correspondingly) to the fit for T = 180 K. Inset: the temperature variation of mean particle moment ⟨μP⟩(T) (symbols) and the solid curve is the Bloch's T3/2 law.
The temperature dependences of magnetic moment M(T) in field H = 1 kOe (left scale) and integral intensity of the ESR spectrum (right scale) of 05FS sample in the range up to 900 K. Inset: typical ESR spectra of 05FS sample obtained at different temperatures.
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