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

• Published in: Nanoscale research letters 2013-10, Vol.8 (1), p.446-446, Article 446
• Main Authors: He, Xuemin, Zhong, Wei, Au, Chak-Tong, Du, Youwei
• Format: Article
• Language: English
• Subjects: Chemistry and Materials Science; Materials Science; Molecular Medicine; Nano Express; Nanochemistry; Nanoscale Science and Technology; Nanotechnology; Nanotechnology and Microengineering
• ISSN: 1931-7573; 1556-276X; 1556-276X
• DOI: 10.1186/1556-276X-8-446

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 T C 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 T C . The measurement of magnetic hysteresis loop reveals that the saturation magnetization M S 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 M S 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.