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Determination of anisotropy constants of protein encapsulated iron oxide nanoparticles by electron magnetic resonance |
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| Authors: | Hongyan Li Michael T. Klem Karl B. Sebby David J. Singel Mark Young Trevor Douglas Yves U. Idzerda |
| Affiliation: | a Department of Physics, Montana State University, Bozeman, MT 59717, USA b Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA c Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717, USA d Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717, USA |
| Abstract: | Angle-dependent electron magnetic resonance was performed on 4.9, 8.0, and 19 nm iron oxide nanoparticles encapsulated within protein capsids and suspended in water. Measurements were taken at liquid nitrogen temperature after cooling in a 1 T field to partially align the particles. The angle dependence of the shifts in the resonance field for the iron oxide nanoparticles (synthesized within Listeria-Dps, horse spleen ferritin, and cowpea chlorotic mottle virus) all show evidence of a uniaxial anisotropy. Using a Boltzmann distribution for the particles’ easy-axis direction, we are able to use the resonance field shifts to extract a value for the anisotropy energy, showing that the anisotropy energy density increases with decreasing particle size. This suggests that surface anisotropy plays a significant role in magnetic nanoparticles of this size. |
| Keywords: | 76.50.+g 75.75.+a 75.30.Gw |
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