The influence of collective behavior on the magnetic and heating properties of iron oxide nanoparticles

C. L. Dennis, A. J. Jackson, J. A. Borchers, R. Ivkov, A. R. Foreman, J. W. Lau, E. Goernitz, C. Gruettner

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80 Scopus citations


Magnetic nanoparticles with a high specific absorption rate (SAR) have been developed and used in mouse models of cancer. The magnetic nanoparticles are comprised of predominantly iron oxide magnetic cores surrounded by a dextran layer for colloidal stability. The average diameter of a single particle (core plus dextran) is 92±14 nm as measured by photon correlation spectroscopy. Small angle neutron scattering measurements under several H2 O D2 O contrast conditions and at varying nanoparticle concentrations have revealed three length scales: >10 μm, several hundred nanometers, and tens of nanometers. The latter corresponds to the particle diameter; the several hundred nanometers corresponds to a hard sphere interaction radius of the core/shell nanoparticles; >10 μm corresponds to the formation of long-range, many-particle structures held together by magnetic interactions and dextran. The long-range collective magnetic behavior appears to play a major role in enhancing the SAR. For samples having nominally equal concentrations and similar saturation magnetizations, the measured SAR is 1075 W /(g of Fe) for tightly associated nanoparticles and 150 W /(g of Fe) for very loosely associated nanoparticles at an applied field of 86 kAm (1080 Oe) and 150 kHz.

Original languageEnglish (US)
Article number07A319
JournalJournal of Applied Physics
Issue number7
StatePublished - 2008
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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