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Synthesis, magnetic and optical properties of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles.

Girgis E, Wahsh MM, Othman AG, Bandhu L, Rao K - Nanoscale Res Lett (2011)

Bottom Line: It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases.On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles.These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications.

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Affiliation: Solid State Physics Department, National Research Centre, 12311 Dokki, Giza, Egypt. egirgis@gmail.com.

ABSTRACT
The optical properties of multi-functionalized cobalt ferrite (CoFe2O4), cobalt zinc ferrite (Co0.5Zn0.5Fe2O4), and zinc ferrite (ZnFe2O4) nanoparticles have been enhanced by coating them with silica shell using a modified Stöber method. The ferrites nanoparticles were prepared by a modified citrate gel technique. These core/shell ferrites nanoparticles have been fired at temperatures: 400°C, 600°C and 800°C, respectively, for 2 h. The composition, phase, and morphology of the prepared core/shell ferrites nanoparticles were determined by X-ray diffraction and transmission electron microscopy, respectively. The diffuse reflectance and magnetic properties of the core/shell ferrites nanoparticles at room temperature were investigated using UV/VIS double-beam spectrophotometer and vibrating sample magnetometer, respectively. It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases. The cobalt ferrite nanoparticles fired at temperature 800°C; show the highest saturation magnetization while the zinc ferrite nanoparticles coated with silica shell shows the highest diffuse reflectance. On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles. These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications.

No MeSH data available.


Hysteresis loops of Co0.5Zn0.5Fe2O4 nanoparticles uncoated (a) and coated with silica shell (b).
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Figure 4: Hysteresis loops of Co0.5Zn0.5Fe2O4 nanoparticles uncoated (a) and coated with silica shell (b).

Mentions: The hysteresis loops of cobalt zinc ferrite nanoparticles (Co0.5Zn0.5Fe2O4) uncoated and coated fired at 400°C and 800°C are shown in Figure 4. When the Co2+ ions in cobalt ferrite samples is substituted by Zn2+ ions (Co0.5Zn0.5Fe2O4 and ZnFe2O4), the magnetization saturation and the switching field are found to decrease with increasing the concentration of Zn2+ ions. Accordingly, the width of hysteresis loop and the magnetic moment decrease due to the substitution of the magnetic Co element by Zn element which is a non-magnetic material. Core/shell ferrite nanoparticles show lower magnetization saturation than the uncoated ferrite nanoparticles fired at the same temperature, while the switching field increases for the coated ferrite nanoparticles. This is due to the effect of silica shell coating where each particle was separated from its neighbors by the shell layer leading to decrease the magnetostatic coupling between the particles.


Synthesis, magnetic and optical properties of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles.

Girgis E, Wahsh MM, Othman AG, Bandhu L, Rao K - Nanoscale Res Lett (2011)

Hysteresis loops of Co0.5Zn0.5Fe2O4 nanoparticles uncoated (a) and coated with silica shell (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211881&req=5

Figure 4: Hysteresis loops of Co0.5Zn0.5Fe2O4 nanoparticles uncoated (a) and coated with silica shell (b).
Mentions: The hysteresis loops of cobalt zinc ferrite nanoparticles (Co0.5Zn0.5Fe2O4) uncoated and coated fired at 400°C and 800°C are shown in Figure 4. When the Co2+ ions in cobalt ferrite samples is substituted by Zn2+ ions (Co0.5Zn0.5Fe2O4 and ZnFe2O4), the magnetization saturation and the switching field are found to decrease with increasing the concentration of Zn2+ ions. Accordingly, the width of hysteresis loop and the magnetic moment decrease due to the substitution of the magnetic Co element by Zn element which is a non-magnetic material. Core/shell ferrite nanoparticles show lower magnetization saturation than the uncoated ferrite nanoparticles fired at the same temperature, while the switching field increases for the coated ferrite nanoparticles. This is due to the effect of silica shell coating where each particle was separated from its neighbors by the shell layer leading to decrease the magnetostatic coupling between the particles.

Bottom Line: It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases.On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles.These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications.

View Article: PubMed Central - HTML - PubMed

Affiliation: Solid State Physics Department, National Research Centre, 12311 Dokki, Giza, Egypt. egirgis@gmail.com.

ABSTRACT
The optical properties of multi-functionalized cobalt ferrite (CoFe2O4), cobalt zinc ferrite (Co0.5Zn0.5Fe2O4), and zinc ferrite (ZnFe2O4) nanoparticles have been enhanced by coating them with silica shell using a modified Stöber method. The ferrites nanoparticles were prepared by a modified citrate gel technique. These core/shell ferrites nanoparticles have been fired at temperatures: 400°C, 600°C and 800°C, respectively, for 2 h. The composition, phase, and morphology of the prepared core/shell ferrites nanoparticles were determined by X-ray diffraction and transmission electron microscopy, respectively. The diffuse reflectance and magnetic properties of the core/shell ferrites nanoparticles at room temperature were investigated using UV/VIS double-beam spectrophotometer and vibrating sample magnetometer, respectively. It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases. The cobalt ferrite nanoparticles fired at temperature 800°C; show the highest saturation magnetization while the zinc ferrite nanoparticles coated with silica shell shows the highest diffuse reflectance. On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles. These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications.

No MeSH data available.