Critical dimension for magnetic exchange-spring coupled core/shell nanoparticles

Core/shell nanoparticles of CoFe 2 O 4 / CoFe 2 were prepared by reducing nanoparticles of CoFe 2 O 4 under hydrogen atmospheres. The structure, morphology and room temperature magnetization of the core/shell nanoparticles were analyzed by X-ray diffraction, transmission electron microscopy and magn...

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Bibliographic Details
Published inJournal of magnetism and magnetic materials Vol. 326; pp. 81 - 84
Main Authors Soares, J M, Galdino, V B, Conceicao, OLA, Morales, MA, de Araujo, JH, Machado, FLA
Format Journal Article
LanguageEnglish
Published 01.01.2013
Subjects
Couples
Diffraction
Exchange
Magnetization
Nanoparticles
Particle size
Shells
X-rays
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Summary:Core/shell nanoparticles of CoFe 2 O 4 / CoFe 2 were prepared by reducing nanoparticles of CoFe 2 O 4 under hydrogen atmospheres. The structure, morphology and room temperature magnetization of the core/shell nanoparticles were analyzed by X-ray diffraction, transmission electron microscopy and magnetometry, respectively. The sample preparation procedure allowed the diameter of the CoFe 2 O 4 core to be varied from 67.7 to 2.8 nm. From the magnetic data it was found that the core couples to the shell through the exchange-spring mechanism while the critical thickness of the soft phase (shell) was estimated using a current theoretical model to be 8.0 nm. This value is very close to the one (7.8 nm) obtained for nanoparticles with same composition but obtained using different synthesis route and having an average particle size (32 nm) less than half of the value estimated (73 nm) for the samples investigated in the present work.
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ISSN:0304-8853