Synthesis, structure, and room-temperature ferromagnetism of Ni-doped ZnO nanoparticles
2007
Huang, G. J. | Wang, J. B. | Zhong, X. L. | Zhou, G. C. | Yan, H. L.
In this paper, Ni-doped ZnO (Zn₁₋ₓNiₓO, in which 0 ≤ x ≤ 0.05) diluted magnetic semiconductors nanoparticles are prepared by an ultrasonic assisted sol–gel process. Transmission electron microscopy shows sphere-like nanoparticles with an average size of about 25 nm. From the analysis of X-ray diffraction, the Ni-doped ZnO nanoparticles are identified to be a wurtzite structure, but impurity phases are observed when the Ni content x reaches 0.05. Sample structures are further studied by Raman spectra, from which a broad and strong Raman band in the range of 500–600 cm⁻¹ is observed in Zn₁₋ₓNiₓO. With the increment of x, wurtzite structures degrade gradually. The magnetic properties are measured using superconducting quantum interference device at room temperature; the Zn₁₋ₓNiₓO (x ≤ 0.02) nanoparticles show ferromagnetism. However, for the sample of Zn₀.₉₅Ni₀.₀₅O, paramagnetism is observed, which may be ascribed to ferromagnetic–antiferromagnetic competition.
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