Abstract
High-quality NiFe2O4 nanosized powders were prepared by a new route
using a natural proteic solution of coconut water and metal ions. The
transition from the superparamagnetic to the fernmagnetic state was
observed with the increase of the heat-treatment temperature from 400
degrees C to 800 degrees C.
In this work, Electron Paramagnetic Resonance (EPR), a.c. magnetic
susceptibility(chi(ac)) measurements, infrared (FT-IR) and Raman
spectroscopy have been employed to obtain additional information about
the structural evolution of the NiFe2O4 nanoparticles, with the increase
of the heat-treatment temperature. The obtained results show that the
heat-treatment temperature makes remarkable changes in the structure of
the samples. The NiFe2O4 nanocrystallite samples, treated at 1200
degrees C, exhibit a large a c magnetic susceptibility which was related
with the formation of a mixed spinel phase. This is in agreement with
the Mossbauer spectroscopy results The increase of the volume of the
nickel ferrite leads to an increase of the magnetic susceptibility. The
magnetic properties of these nanoparticles are clearly size dependent.
(C) 2009 Elsevier B.V. All rights reserved.
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