Superparamagnetism in iron-doped CeO₂-y nanocrystals.
We have measured the magnetization of undoped and Fe(2+/3+) doped CeO(2-y) nanocrystals at various temperatures and magnetic fields. The Stoner condition N(0)I > 1 is multiply fulfilled in the case of nano-CeO(2-y), favoring the band ferromagnetism approach. In the case of Fe-doped samples, the magnetization versus magnetic field dependence is well fitted with a weighted Langevin function. A blocking temperature of about 20 K is obtained both from the ZFC/FC curves and from the coercive field against temperature dependence. The temperature and field dependence of the magnetization clearly shows the presence of nanosized particles which exhibit superparamagnetic behavior.
Center for Solid State Physics and New Materials, Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia.
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Paunović
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Popović
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Dohčević-Mitrović