Journal
NANOSCALE RESEARCH LETTERS
Volume 8, Issue -, Pages -Publisher
SPRINGEROPEN
DOI: 10.1186/1556-276X-8-446
Keywords
Size dependence; Curie temperature; Cohesive energy; Magnetically inactive layer
Funding
- National Natural Science Foundation of China [11174132]
- National Key Project for Basic Research [2011CB922102, 2012CB932304]
- PAPD, People's Republic of China
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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 degrees C, 346 degrees C, 351 degrees C, and 354 degrees 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.
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