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Size dependence of the magnetic properties of Ni nanoparticles prepared by thermal decomposition method.

He X, Zhong W, Au CT, Du Y - Nanoscale Res Lett (2013)

Bottom Line: The measurement of magnetic hysteresis loop reveals that the saturation magnetization MS and remanent magnetization increase and the coercivity decreases monotonously with increasing particle size, indicating a distinct size effect.By adopting a simplified theoretical model, we obtained MS values that are in good agreement with the experimental ones.Furthermore, with increase of surface-to-volume ratio of Ni nanoparticles due to decrease of particle size, there is increase of the percentage of magnetically inactive layer.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Department of Physics, Nanjing University, Nanjing 210093, China. wzhong@nju.edu.cn.

ABSTRACT
By means of thermal decomposition, we prepared single-phase spherical Ni nanoparticles (23 to 114 nm in diameter) that are face-centered cubic in structure. The magnetic properties of the Ni nanoparticles were experimentally as well as theoretically investigated as a function of particle size. By means of thermogravimetric/differential thermal analysis, the Curie temperature TC of the 23-, 45-, 80-, and 114-nm Ni particles was found to be 335°C, 346°C, 351°C, and 354°C, respectively. Based on the size-and-shape dependence model of cohesive energy, a theoretical model is proposed to explain the size dependence of TC. The measurement of magnetic hysteresis loop reveals that the saturation magnetization MS and remanent magnetization increase and the coercivity decreases monotonously with increasing particle size, indicating a distinct size effect. By adopting a simplified theoretical model, we obtained MS values that are in good agreement with the experimental ones. Furthermore, with increase of surface-to-volume ratio of Ni nanoparticles due to decrease of particle size, there is increase of the percentage of magnetically inactive layer.

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SEM images. Ni nanoparticles formed at (a) 240°C, (b) 255°C, (c) 270°C, and (d) 285°C.
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Figure 2: SEM images. Ni nanoparticles formed at (a) 240°C, (b) 255°C, (c) 270°C, and (d) 285°C.

Mentions: Figure 2 shows the representative SEM images of the Ni nanoparticles formed at 240°C, 255°C, 270°C, and 285°C. It is observed that most Ni particles are oval or spherical in shape. The particle-size analysis based on SEM images shows normal Gaussian distributions (Figure 3). It is apparent that the mean particle size increases with increasing reaction temperature, in excellent agreement with the results of XRD analysis. Hereinafter, D denotes the mean particle sizes which are 23, 45, 80, and 114 nm for the samples formed at 240°C, 255°C, 270°C, and 285°C, respectively, and the symbol ‘Δ’ denotes the absolute deviation obtained from the Gaussian fitting. It can be seen that the absolute deviation increases with the increase of mean particle size. It is reasonable to deduce that the change of reaction temperature will result in density difference of organic functional groups on the particle surface [31]. We propose that the control of reaction temperature is a mean for easy regulation of particle size and size distribution during the growth process.


Size dependence of the magnetic properties of Ni nanoparticles prepared by thermal decomposition method.

He X, Zhong W, Au CT, Du Y - Nanoscale Res Lett (2013)

SEM images. Ni nanoparticles formed at (a) 240°C, (b) 255°C, (c) 270°C, and (d) 285°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231360&req=5

Figure 2: SEM images. Ni nanoparticles formed at (a) 240°C, (b) 255°C, (c) 270°C, and (d) 285°C.
Mentions: Figure 2 shows the representative SEM images of the Ni nanoparticles formed at 240°C, 255°C, 270°C, and 285°C. It is observed that most Ni particles are oval or spherical in shape. The particle-size analysis based on SEM images shows normal Gaussian distributions (Figure 3). It is apparent that the mean particle size increases with increasing reaction temperature, in excellent agreement with the results of XRD analysis. Hereinafter, D denotes the mean particle sizes which are 23, 45, 80, and 114 nm for the samples formed at 240°C, 255°C, 270°C, and 285°C, respectively, and the symbol ‘Δ’ denotes the absolute deviation obtained from the Gaussian fitting. It can be seen that the absolute deviation increases with the increase of mean particle size. It is reasonable to deduce that the change of reaction temperature will result in density difference of organic functional groups on the particle surface [31]. We propose that the control of reaction temperature is a mean for easy regulation of particle size and size distribution during the growth process.

Bottom Line: The measurement of magnetic hysteresis loop reveals that the saturation magnetization MS and remanent magnetization increase and the coercivity decreases monotonously with increasing particle size, indicating a distinct size effect.By adopting a simplified theoretical model, we obtained MS values that are in good agreement with the experimental ones.Furthermore, with increase of surface-to-volume ratio of Ni nanoparticles due to decrease of particle size, there is increase of the percentage of magnetically inactive layer.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Department of Physics, Nanjing University, Nanjing 210093, China. wzhong@nju.edu.cn.

ABSTRACT
By means of thermal decomposition, we prepared single-phase spherical Ni nanoparticles (23 to 114 nm in diameter) that are face-centered cubic in structure. The magnetic properties of the Ni nanoparticles were experimentally as well as theoretically investigated as a function of particle size. By means of thermogravimetric/differential thermal analysis, the Curie temperature TC of the 23-, 45-, 80-, and 114-nm Ni particles was found to be 335°C, 346°C, 351°C, and 354°C, respectively. Based on the size-and-shape dependence model of cohesive energy, a theoretical model is proposed to explain the size dependence of TC. The measurement of magnetic hysteresis loop reveals that the saturation magnetization MS and remanent magnetization increase and the coercivity decreases monotonously with increasing particle size, indicating a distinct size effect. By adopting a simplified theoretical model, we obtained MS values that are in good agreement with the experimental ones. Furthermore, with increase of surface-to-volume ratio of Ni nanoparticles due to decrease of particle size, there is increase of the percentage of magnetically inactive layer.

No MeSH data available.


Related in: MedlinePlus