期刊
CHINESE PHYSICS B
卷 22, 期 10, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1674-1056/22/10/107101
关键词
Mn ferrite; magnetic materials; hydrothermal method; superparamagnetic; Raman spectroscopy
资金
- National Natural Science Foundation of China [50472092, 50672008, 50971023]
- Beijing Natural Science Foundation
- Research Foundation for Talented Scholars of China Three Gorges University
- University of Science and Technology of Beijing
Highly dispersive nanospheres of MnFe2O4 are prepared by template free hydrothermal method. The nanospheres have 47.3-nm average diameter, narrow size distribution, and good crystallinity with average crystallite size about 22 nm. The reaction temperature strongly affects the morphology, and high temperature is found to be responsible for growth of uniform nanospheres. Raman spectroscopy reveals high purity of prepared nanospheres. High saturation magnetization (78.3 emu/g), low coercivity (45 Oe, 1 Oe = 79.5775 A.cm(-1)), low remanence (5.32 emu/g), and high anisotropy constant 2.84 x 10(4) J/m(3) (10 times larger than bulk) are observed at room temperatures. The nearly superparamagnetic behavior is due to comparable size of nanospheres with superparamagnetic critical diameter D-cr(spm). The high value of K-eff may be due to coupling between the pinned moment in the amorphous shell and the magnetic moment in the core of the nanospheres. The nanospheres show prominent optical absorption in the visible region, and the indirect band gap is estimated to be 0.98 eV from the transmission spectrum. The prepared Mn ferrite has potential applications in biomedicine and photocatalysis.
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