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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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XRD patterns (a) and HRTEM image (b). Ni nanoparticles formed at (a) 240°C, (b) 255°C, (c) 270°C, and (d) 285°C. SAED pattern and HRTEM image relative to Ni nanoparticles formed at 255°C.
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Figure 1: XRD patterns (a) and HRTEM image (b). Ni nanoparticles formed at (a) 240°C, (b) 255°C, (c) 270°C, and (d) 285°C. SAED pattern and HRTEM image relative to Ni nanoparticles formed at 255°C.

Mentions: Figure 1a shows the powder XRD patterns of the Ninanoparticle samples synthesized at 240°C, 255°C, 270°C, and 285°C. All samples are single-phase with face-centered cubic (fcc) structure, and no phase of NiO or other impurity is observed. The three obvious peaks (2θ = 44.58°, 51.90°, 76.54°) can be assigned to the (111), (200), and (220) planes of Ni crystal lattice, respectively. It is clear that there is peak broadening upon decrease of reaction temperature. In other words, the particle size of the prepared Ni nanoparticles increases with increasing reaction temperature, and this is confirmed in SEM analysis (show later). As can be seen in the SAED pattern (inset of Figure 1a), perfect cubic symmetry can be clearly identified for the polycrystalline Ni nanoparticles. The high-resolution TEM image in Figure 1b presents the granular morphology and further reveals the surface nature of magnetically dead layer.


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)

XRD patterns (a) and HRTEM image (b). Ni nanoparticles formed at (a) 240°C, (b) 255°C, (c) 270°C, and (d) 285°C. SAED pattern and HRTEM image relative to Ni nanoparticles formed at 255°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: XRD patterns (a) and HRTEM image (b). Ni nanoparticles formed at (a) 240°C, (b) 255°C, (c) 270°C, and (d) 285°C. SAED pattern and HRTEM image relative to Ni nanoparticles formed at 255°C.
Mentions: Figure 1a shows the powder XRD patterns of the Ninanoparticle samples synthesized at 240°C, 255°C, 270°C, and 285°C. All samples are single-phase with face-centered cubic (fcc) structure, and no phase of NiO or other impurity is observed. The three obvious peaks (2θ = 44.58°, 51.90°, 76.54°) can be assigned to the (111), (200), and (220) planes of Ni crystal lattice, respectively. It is clear that there is peak broadening upon decrease of reaction temperature. In other words, the particle size of the prepared Ni nanoparticles increases with increasing reaction temperature, and this is confirmed in SEM analysis (show later). As can be seen in the SAED pattern (inset of Figure 1a), perfect cubic symmetry can be clearly identified for the polycrystalline Ni nanoparticles. The high-resolution TEM image in Figure 1b presents the granular morphology and further reveals the surface nature of magnetically dead layer.

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