Size dependence of the magnetic properties of Ni nanoparticles prepared by thermal decomposition method
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NANO EXPRESS
Open Access
Size dependence of the magnetic properties of Ni nanoparticles prepared by thermal decomposition method Xuemin He1, Wei Zhong1*, Chak-Tong Au2 and Youwei Du1
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. Keywords: Size dependence; Curie temperature; Cohesive energy; Magnetically inactive layer
Background The transition metal nickel shows distinct magnetic and catalytic properties [1,2]. In nanostructure, Ni has great application potential in fields such as pharmaceutical synthesis [3], magnetic biocatalysis [4], biomolecular separation [5], and biosensor [6]. In the literatures, there are reports on the preparation and properties of novel Ni nanomaterials such as sea urchin-like Ni nanoparticles [7], tetragonal Ni nanoparticles [8], hexagonal closepacked (hcp) Ni nanoparticles [9], conical Ni nanorods [10], triangular and hexagonal Ni nanosheets [11], and Ni nanochains [12]. It is known that the performance of technological devices is greatly influenced by the purity, structure, shape, and size of Ni nanoparticles. Hence, it is of great significance to prepare high-quality Ni nanomaterials of specificity using convenient and low-cost methods. * Correspondence: [email protected] 1 National Laboratory of Solid State Microstructures and Jiangsu Provincial Laboratory for NanoTechnology, Department of Physics, Nanjing University, Nanjing 210093, China Full list of author information is available at the end of the article
For the fabrication of Ni nanoparticles, methods such as sputtering [13,14], solution glow discharge [15], pulsed laser ablation [6], reversed micelles [16], thermal decomposition [17-20], and wet chemical reduction [7,21,22] are used. Among them, the ones based on thermal decomposition are preferred. The single-step process is facile, environment-benign, inexpensive, and reproducible, yielding high-quality Ni powders that can be controlled in terms of structure, morphology, si
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