الفهرس 
Theoretical Background
Fundamental Theory of MagnetismOnly 14 pages are availabe for public view
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Abstract
The main interest of this thesis is to study the effect of coreshell
structure on the magnetic properties of CoFe2O4 magnetic
particles with dimensions in the nanometer range. Four samples
have been investigated, as follows: (I) CoFe2O4 magnetic
nanoparticle (II) CoFe2O4-NiFe2O4 core-shell magnetic
nanocomposite (III) CoFe2O4-ZnFe2O4 core-shell magnetic
nanocomposite (IV) CoFe2O4-ZnFe2O4-NiFe2O4 core-shell-shell
magnetic nanocomposite.
First, we prepared bare cobalt ferrite using hydrothermal method
with particle size 15 nm. Two samples of Hard Ferromagnetism
(FM)-Soft Ferromagnetism (FM) interface, CoFe2O4-NiFe2O4, and
Ferromagnetism (FM)-Antiferromagnetism (AFM) interface,
CoFe2O4-ZnFe2O4, as core-shell structure are prepared. X-ray
diffraction (XRD) analysis showed that all samples have cubic
spinel phase.
The evidence of the formation of core-shell structure is
satisfied by many tools such as Fourier transform infrared (FT-IR)
spectrum, high-resolution transmission electron microscopy (HRTEM)
and energy dispersive X-ray (EDX) analysis. The thickness
of the shell was found to be about 3 nm.
The presence of, soft FM, NiFe2O4 as a shell has great effect on the
different magnetic properties of CoFe2O4 such as:
Enhanced in saturation magnetization about 17%.
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Decreasing in coercive field (Hc) by about 5%.
Presence of blocking temperature at 480 K.
Increasing of magnetization with temperature and
increasing the effective anisotropy field.
Also, the formation of, AFM, ZnFe2O4 as a shell also shows
very good modification in the magnetic properties of CoFe2O4. The
most important results could be summarized as follows:
The saturation magnetization increases slightly.
The coercive field becomes almost zero at room
temperature (super paramagnetic).
Low temperature measurements of magnetization
loops show strong exchange biasing interaction at the
interface between ZnFe2O4 and CoFe2O4.
The blocking temperature at 261 K.
Decreasing of magnetization with increasing
temperature.
Multi shell of (Hard FM-AFM-Soft FM) CoFe2O4-ZnFe2O4-
NiFe2O4 was prepared and the effect of this new composite on the
magnetic properties is studied. The most important results could be
summarized as follows:
XRD, FT-IR and TEM measurements prove the presence
of the multi shell structure.
Great enhancement in the magnetization.
Decreasing in Hc.
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New magnetic transition at 513 K.
The measurements of hysteresis parameters at low
temperature show increasing in the magnetization with
increasing temperature.
One of the most important recent applications is the use of
CoFe2O4 nano in hyperthermia for cancer treatment because of its
high specific absorption rate (SAR). In this work, it was proved
that the presence of magnetic shell on the surface of CoFe2O4
enhances the SAR value, especially the multi shell structure.