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Alignment under Magnetic Field of Mixed Fe 2 O 3 /SiO 2 Colloidal Mesoporous Particles Induced by Shape Anisotropy
Author(s) -
Li JhengGuang,
Fornasieri Giulia,
Bleuzen Anne,
Gich Martí,
Gloter Alexandre,
Bouquet Frédéric,
ImpérorClerc Marianne
Publication year - 2016
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201602272
Subject(s) - materials science , anisotropy , nanocomposite , superparamagnetism , mesoporous material , nanocrystal , iron oxide , phase (matter) , oxide , magnetic anisotropy , nanotechnology , chemical engineering , magnetic field , magnetization , metallurgy , chemistry , optics , biochemistry , physics , organic chemistry , engineering , quantum mechanics , catalysis
When using the bottom‐up approach with anisotropic building‐blocks, an important goal is to find simple methods to elaborate nanocomposite materials with a truly macroscopic anisotropy. Here, micrometer size colloidal mesoporous particles with a highly anisotropic rod‐like shape (aspect ratio ≈ 10) have been fabricated from silica (SiO 2 ) and iron oxide (Fe 2 O 3 ). When dispersed in a solvent, these particles can be easily oriented using a magnetic field (≈200 mT). A macroscopic orientation of the particles is achieved, with their long axis parallel to the field, due to the shape anisotropy of the magnetic component of the particles. The iron oxide nanocrystals are confined inside the porosity and they form columns in the nanochannels. Two different polymorphs of Fe 2 O 3 iron oxide have been stabilized, the superparamagnetic γ‐phase and the rarest multiferroic ε‐phase. The phase transformation between these two polymorphs occurs around 900 °C. Because growth occurs under confinement, a preferred crystallographic orientation of iron oxide is obtained, and structural relationships between the two polymorphs are revealed. These findings open completely new possibilities for the design of macroscopically oriented mesoporous nanocomposites, using such strongly anisotropic Fe 2 O 3 /silica particles. Moreover, in the case of the ε‐phase, nanocomposites with original anisotropic magnetic properties are in view.