Aggregation state and magnetic properties of magnetite nanoparticles controlled by an optimized silica coating

The control of magnetic interactions is becoming essential to expand/improve the applicability of magnetic nanoparticles (NPs). Here, we show that an optimized microemulsion method can be used to obtain homogenous silica coatings on even single magnetic nuclei of highly crystalline Fe3−xO4 NPs (7 an...

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Bibliographic Details
Published in:Journal of applied physics 2017-01, Vol.121 (4)
Main Authors: Pérez, Nicolás, Moya, C., Tartaj, P., Labarta, A., Batlle, X.
Format: Article
Language:English
Subjects:
Applied physics
Coating effects
Dipoles
Energy distribution
Magnetic permeability
Magnetic properties
Magnetism
Nanoparticles
Oleic acid
Quantitative analysis
Silicon dioxide
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Summary:The control of magnetic interactions is becoming essential to expand/improve the applicability of magnetic nanoparticles (NPs). Here, we show that an optimized microemulsion method can be used to obtain homogenous silica coatings on even single magnetic nuclei of highly crystalline Fe3−xO4 NPs (7 and 16 nm) derived from a high-temperature method. We show that the thickness of this coating is controlled almost at will allowing much higher average separation among particles as compared to the oleic acid coating present on pristine NPs. Magnetic susceptibility studies show that the thickness of the silica coating allows the control of magnetic interactions. Specifically, as this effect is better displayed for the smallest particles, we show that dipole-dipole interparticle interactions can be tuned progressively for the 7 nm NPs, from almost non-interacting to strongly interacting particles at room temperature. The quantitative analysis of the magnetic properties unambiguously suggests that dipolar interactions significantly broaden the effective distribution of energy barriers by spreading the distribution of activation magnetic volumes.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4974532