Room temperature ferromagnetism of ZnO nanocrystals in amorphous ZnO–Al2O3 matrix

Ma, Y. W.; Ding, J.; Qi, D. C.; Yi, J. B.; Fan, H. M.; Gong, H.; Wee, A. T. S.; Rusydi, A.
August 2009
Applied Physics Letters;8/17/2009, Vol. 95 Issue 7, p072501
Academic Journal
In this work, we demonstrate room temperature ferromagnetism of ZnO nanocrystals (NCs) embedded in alumina-based amorphous matrix. Our study has shown that solid solution occurred for lower Al concentration [≤x=0.09 for (Zn1-x,Alx)O]. No ferromagnetism appears in Al-doped ZnO with x≤0.09. With higher Al concentration, alumina-based amorphous structure appeared and fully amorphous was found in the composition of (Zn0.30,Al0.70)O. Ferromagnetism was found in (Zn1-x,Alx)O with a threshold of 16 mol % of Al. The room temperature ferromagnetism was found to be attributed to ZnO NCs in an alumina-based amorphous ZnO–Al2O3 matrix. Ferromagnetism reached a maximum with a volume percentage of ZnO NCs to be ∼27 vol %. The detailed investigations (transmission electron microscopy, x-ray photoelectron spectroscopy, and superconducting quantum interference device) show that the optimized size of these NCs is in the range of 4–5 nm. No ferromagnetism appears if the sample contains a fully amorphous structure.


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