Magnetic properties and microstructure of cobalt nanoparticles in a polymer film |
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Authors: | I-W Park M YoonYM Kim Y KimH Yoon HJ SongV Volkov A AvilovYJ Park |
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Institution: | a Structure analysis team, Korea Basic Science Institute, 126-16, Anam-Dong, Sungbuk-Ku, Seoul 136701, South Korea b Nano Device Research Center, KIST, P.O. Box 131, Cheongryang, Seoul 130-650, South Korea |
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Abstract: | Superparamagnetic properties of self-aggregated cobalt nanoparticles in the perfluorinated sulfo-cation membrane (MF-4SK) prepared by ion-exchange method were investigated by transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID) magnetometry at various temperatures. Our experimental results show that cobalt nanoparticles in MF-4SK exhibit superparamagnetic properties above the blocking temperature (TB), which varies from ∼80 to ∼300 K depending on the cobalt concentration at 100 Oe applied field. The average particle radius of 3.8 nm inferred from Langevin function fit for the concentration of 7.8×1019 cobalt atoms per 1 g of polymer film is in good agreement with TEM observation. This experimental evidence suggests that cobalt nanoparticles in the polymer film obey a single-domain theory. The results are discussed in the light of current theory for the superparamagnetic behavior of magnetic nanoparticles. |
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Keywords: | 75 20 &minus g 75 75 +a 75 50 Ss |
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