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Publication Citation: Ripening during magnetite nanoparticle synthesis: Resulting interfacial defects and magnetic properties

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Author(s): Alexander J. Barker; Brant Cage; Stephen E. Russek; Conrad Stoldt;
Title: Ripening during magnetite nanoparticle synthesis: Resulting interfacial defects and magnetic properties
Published: October 03, 2005
Abstract: The structure and magnetic properties of magnetite (Fe3O4) nanoparticles synthesized by a solvothermal processing route are investigated. The nanoparticles are grown from the single organometallic precursor Fe(III) acetylacetonate in trioctylamine (TOA) solvent at 260°C, with and without the addition of heptanoic acid (HA) as a stabilizing agent. From the temporal particle size distributions, x-ray-diffraction patterns, high-resolution transmission electron microscope tilt series experiments, and superconducting quantum interference device magnetometry, we demonstrate that HA, a strong Lewis acid stabilizing agent, slows growth processes during ripening thus reducing the formation of interfacial defects, which we observe in the TOA-only synthesis. Nanoparticles grown with HA remain single-crystalline for long growth times (up to 24 h), show a focused particle size distribution for intermediate growth times (3 h), and possess a higher magnetic anisotropy (15.8 x 104 J/m3) than particles grown without the additional stabilizing agent. The reduced magnetic anisotropy value for the magnetite nanoparticles grown in TOA-only (1.29 x 104 J/m3) is attributed to polycrystallinity induced by the uncontrolled ripening process. This work may have significance for contrast enhancement in magnetic resonance imaging.
Citation: Journal of Applied Physics
Volume: 98
Issue: 063528
Pages: pp. 1 - 7
Keywords: iron oxide;magnetic susceptibility;nanoparticle
Research Areas: Electromagnetics
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