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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.

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.


Hysteresis loops of CoFe2O4 nanoparticles uncoated (a) and coated with silica shell (b).
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Figure 3: Hysteresis loops of CoFe2O4 nanoparticles uncoated (a) and coated with silica shell (b).

Mentions: The hysteresis loops and the magnetic parameters (saturation magnetization (Ms) and switching field (Hc)) of the prepared ferrite nanoparticles fired at 400°C and 800°C were measured at room temperature (27°C) using vibrating samples magnetometer. Figure 3a shows the hysteresis loops of uncoated cobalt ferrite nanoparticles fired at 400°C and 800°C. It is clear that by increasing the firing temperature from 400°C to 800°C, the Ms increased from 56.7 to 79.37 emu/g and the Hc decreased from 1009.5 to 131.3 Oe. Increasing the firing temperature leads to increase the crystal size of the ferrite nanoparticles which reflects on the magnetization state by creating a multidomains state instead of single-domain state. Multidomains need less magnetic field to switch compared with the single domain state. Accordingly, it was found that at large crystallite size, the switching field decreases and the magnetization saturation increases compared with the smaller size. Figure 3b shows the hysteresis loops of the coated cobalt ferrite nanoparticles fired at 400°C and 800°C where a slight decrease in the saturation magnetization compared with the uncoated nanoparticles was observed. The slight decrease in the magnetization saturation and increase in the switching field is due to the coating effect, where each particle was separated from its neighbors with silica shell which leads to decrease the magnetostatic coupling between the particles. By increasing the firing temperature to 800°C, the crystals will grow leading to increase the magnetization saturation and create a multidomains state.


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 CoFe2O4 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 3: Hysteresis loops of CoFe2O4 nanoparticles uncoated (a) and coated with silica shell (b).
Mentions: The hysteresis loops and the magnetic parameters (saturation magnetization (Ms) and switching field (Hc)) of the prepared ferrite nanoparticles fired at 400°C and 800°C were measured at room temperature (27°C) using vibrating samples magnetometer. Figure 3a shows the hysteresis loops of uncoated cobalt ferrite nanoparticles fired at 400°C and 800°C. It is clear that by increasing the firing temperature from 400°C to 800°C, the Ms increased from 56.7 to 79.37 emu/g and the Hc decreased from 1009.5 to 131.3 Oe. Increasing the firing temperature leads to increase the crystal size of the ferrite nanoparticles which reflects on the magnetization state by creating a multidomains state instead of single-domain state. Multidomains need less magnetic field to switch compared with the single domain state. Accordingly, it was found that at large crystallite size, the switching field decreases and the magnetization saturation increases compared with the smaller size. Figure 3b shows the hysteresis loops of the coated cobalt ferrite nanoparticles fired at 400°C and 800°C where a slight decrease in the saturation magnetization compared with the uncoated nanoparticles was observed. The slight decrease in the magnetization saturation and increase in the switching field is due to the coating effect, where each particle was separated from its neighbors with silica shell which leads to decrease the magnetostatic coupling between the particles. By increasing the firing temperature to 800°C, the crystals will grow leading to increase the magnetization saturation and create a multidomains state.

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.