increase of ferromagnetic ordering by Cu doping in Zn1-xCoxO system

Hoang, Luc Huy1; Khoi, Nguyen The1; Hai, Nguyen Hoang1; Yang, In-Sang2 1Vietnam; 2Republic of Korea

Cu doped Zn_1-xCo_xO powders were prepared using sol-gel method. The x-ray diffraction data confirmed that the wurtzite structure of ZnO is maintained for the ZnO doped with Co below 10% at. However, Raman spectra of the doped ZnO show additional phonon modes beyond 5% at. of Co. Therefore, we chose a system of Zn_0.098Co_0.02O and studied the effect of Cu doping, the Cu content from 0 to 1% at. Without Cu-doping, a pure paramagnetic behavior is observed in the Zn_0.098Co_0.02O. On the other hand, a ferromagnetic ordering is observed (by VSM) for the Cu-doped Zn_0.098Co_0.02O systems, and the ordering seems to be stronger as the Cu-content increase. The relative strength of the LO mode and its second order peak of the Cu-doped Zn_0.098Co_0.02O increases as the Cu-doping content, which seems to be correlated with the increase of the ferromagnetic ordering. Study of the effect of Cu-doping on the LO mode of the Zn_0.098Co_0.02O would give an evidence for the origin of the ferromagnetic behavior in this system.

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