| 1. |
- Salazar-Alvarez, German, et al.
(författare)
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Enhanced coercivity in Co-rich near-stoichiometric CoFe3-xO4+delta nanoparticles prepared in large batches
- 2007
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 19:20, s. 4957-4963
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Tidskriftsartikel (refereegranskat)abstract
- The relationship between the structure and composition with the magnetic properties of near stoichiometric cobalt ferrite nanoparticles CoxFe3-xO4+delta (0.85 < x < 1.1) prepared in large batches with average sizes in the range 60-210 nm has been investigated. Chemical analysis and Rietveld refinement of the X-ray diffraction data in conjunction with Mossbauer spectroscopy allowed us to identify an interplay between particle size, microstructure (concentration of interstitial ions, microstrain, cation arrangement in octahedral and tetrahedral sites), and composition, which sensitively controls the magnetic properties such as coercivity and saturation magnetization. In all cases, cobalt-rich compositions resulted in a higher coercivity, whereas lower degrees of inversion and higher iron contents led to slightly higher saturation magnetization values.
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| 2. |
- Salazar-Alvarez, German, et al.
(författare)
-
Reversible post-synthesis tuning of the superparamagnetic blocking temperature of gamma-Fe2O3 nanoparticles by adsorption and desorption of Co(II) ions
- 2007
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 17:4, s. 322-328
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the post-synthesis adsorption of Co(II) ions on the structural and magnetic properties of maghemite (gamma-Fe2O3) nanoparticles with a mean particle size of about 10 nm has been investigated. It is shown that the step-wise adsorption of Co( II) can controllably increase the blocking temperature, T-B, of the system up to 60 K with respect to that of untreated particles, while neither the particle size nor the particle size distribution are significantly modified. This is accompanied by a four-fold increase in the coercivity, H-C, at low temperatures. Using a selective leaching of the previously adsorbed Co(II) ions the T-B and H-C values of the pristine gamma-Fe2O3 nanoparticles are recovered. Hence, a reversible and controllable tailoring of the magnetic properties (e.g., T-B and H-C) of the gamma-Fe2O3 nanoparticles can be achieved by a simple adsorption and desorption process of Co( II) ions after their synthesis.
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