Different methods have been investigated for the synthesis of magnetic nanoparticles. Control of the particle size, dispersion, purity and stability have been always regarded an issue. In this study magnetite （Fe304...Different methods have been investigated for the synthesis of magnetic nanoparticles. Control of the particle size, dispersion, purity and stability have been always regarded an issue. In this study magnetite （Fe304） superparamagnetic nanoparticles with a size range about 20 nm have been successfully synthesized using chemical co-precipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline media in oxygen-free environment. The sol-gel method has been chose to encapsulate magnetic nanoparticles into silica matrix. The phase structures, morphologies, surface area, functional classes and magnetic properties have been characterized by X-ray diffraction, SEM and AFM, BET, FT-IR and VSM. The results showed that the resultant films, consisting of encapsulated magnetite have crack free and smooth surface with a roughness value 1.5 rim.展开更多
Amorphous CoxC1-x granular films were prepared on n-Si（100） substrate by dc magnetron sputtering. The effects of Co con- centration, film thickness and annealing temperature on the magnetic properties and magnetores...Amorphous CoxC1-x granular films were prepared on n-Si（100） substrate by dc magnetron sputtering. The effects of Co con- centration, film thickness and annealing temperature on the magnetic properties and magnetoresistance （MR） were investigated After annealing at 500℃ for 0.5 hour, the Co（002） peak of the CoxC1-x（x〉2.5 at.%） films was observed, but cracks appeared in the films. Saturation magnetization Ms increased steadily with the increase of Co concentration from 2.5 at.% to 50 at.% and also increased with annealing temperature from room temperature to 400℃. The coercivity of CoxC1-x films was less than 180 Oe. The as-deposited Co2.5C97.5 granular films with 80 nm thickness showed a highly positive MR, up to 15.5% at a magnetic field of 0.8 T, observed at T=300 K when the external magnetic field was perpendicular to the film surface. With increasing film thickness and annealing temperature, the value of MR was found to decrease gradually and changed from positive to neg- ative. The MR effect of the CoxC1-x granular films can be explained by p-n heterojunction theory and interface scattering ef- fect.展开更多
文摘Different methods have been investigated for the synthesis of magnetic nanoparticles. Control of the particle size, dispersion, purity and stability have been always regarded an issue. In this study magnetite （Fe304） superparamagnetic nanoparticles with a size range about 20 nm have been successfully synthesized using chemical co-precipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline media in oxygen-free environment. The sol-gel method has been chose to encapsulate magnetic nanoparticles into silica matrix. The phase structures, morphologies, surface area, functional classes and magnetic properties have been characterized by X-ray diffraction, SEM and AFM, BET, FT-IR and VSM. The results showed that the resultant films, consisting of encapsulated magnetite have crack free and smooth surface with a roughness value 1.5 rim.
基金supported by the National Natural Science Foundation of China (Grant No. U0734001)the Fundamental Research Funds for the Central Universities, South China University Of Technology (Grant No. 2009ZM0247)
文摘Amorphous CoxC1-x granular films were prepared on n-Si（100） substrate by dc magnetron sputtering. The effects of Co con- centration, film thickness and annealing temperature on the magnetic properties and magnetoresistance （MR） were investigated After annealing at 500℃ for 0.5 hour, the Co（002） peak of the CoxC1-x（x〉2.5 at.%） films was observed, but cracks appeared in the films. Saturation magnetization Ms increased steadily with the increase of Co concentration from 2.5 at.% to 50 at.% and also increased with annealing temperature from room temperature to 400℃. The coercivity of CoxC1-x films was less than 180 Oe. The as-deposited Co2.5C97.5 granular films with 80 nm thickness showed a highly positive MR, up to 15.5% at a magnetic field of 0.8 T, observed at T=300 K when the external magnetic field was perpendicular to the film surface. With increasing film thickness and annealing temperature, the value of MR was found to decrease gradually and changed from positive to neg- ative. The MR effect of the CoxC1-x granular films can be explained by p-n heterojunction theory and interface scattering ef- fect.
