Author/Authors :
Park، نويسنده , , I.-W. and Yoon، نويسنده , , M. and Kim، نويسنده , , Y.M. and Kim، نويسنده , , Y. S. Yoon، نويسنده , , H. and Song، نويسنده , , H.J. and Volkov، نويسنده , , V. and Avilov، نويسنده , , A. and Park، نويسنده , , Y.J.، نويسنده ,
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.
