Abstract
The synthesis of mono-dispersed γ-Fe2O3 nanoparticles by mechanochemical processing was demonstrated for the first time, via the solid-state exchange reaction Fe2(SO4) 3 + 3Na2CO3 → Fe2(CO 3)3 + 3Na2SO4 → Fe 2O3 + 3Na2SO4 + 3CO2(g) and subsequent heat treatment at 673 K. The nanoparticles had a volume-weighted mean diameter of 6 nm and a narrow size distribution with the standard deviation of 3 nm. The particles showed a superparamagnetic nature with the superparamagnetic blocking temperature of 56.6 K. The anisotropy constant was 6.0 × 106 erg/cm3, two orders of magnitude larger than the magnetocrystalline anisotropy constant of bulk γ-Fe 2O3. The detailed analysis of the magnetic properties indicated that the γ-Fe2O3 nanoparticles had a core-shell structure, consisting of a ferrimagnetic core of ∼4 nm in diameter having a collinear spin configuration and a magnetically disordered shell of ∼1.2 nm in thickness.
Original language | English |
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Pages (from-to) | 5420-5425 |
Number of pages | 6 |
Journal | Journal of Alloys and Compounds |
Volume | 509 |
Issue number | 17 |
DOIs | |
Publication status | Published - 28 Apr 2011 |
Externally published | Yes |