Preparation And Magnetism Of Ni,Cu Doped ZnO Diluted Magnetic Semiconductors Bulk Samples

Namely Zn_1-xCu_xO and Zn_1-xNi_xO (x=0.01 , 0.02 , 0.04) diluted magnetic semiconductors are prepared with co-precipitation method in this paper, we also have done a research on structure and magnetic properties. Magnetism measures result display that all the samples of Zn_1-xCu_xO are ferromagnetic under room temperature 300K, and a peculiar ferromagnetic behavior of firstly increasing then decreasing is observed with the increasing of doping concentration. For Ni doped ZnO, fine ferromagnetism is observed only when the doping concentration is 4%, the ferromagnetism of other samples are considerably faint. Ferromagnetism is enhanced with the increasing of doping concentration. X-ray diffraction result demonstrates that Zn_1-xCu_xO (x=0.01) is single phase, all the diffraction peaks can be indexed as ZnO. But the second phase are observed when x>0.01, ZnO and CuO coexist in the system. For Ni doped ZnO, the anti-ferromagnetic second phase NiO are observed in all the samples. Considering the structure, the firstly decreasing of ferromagnetism is attributed to the appearance of CuO, the subsequently faint increasing of ferromagnetism is because CuO precipitate in Zn_1-xCu_xO (x=0.02 , 0.04), the enhancement of ferromagnetism followed with the increasing of doping concentration is attributed to the more substitution of Ni2+ for Zn2+.We believe the origin of ferromagnetism is intrinsic, and the ferromagnetism is explained as bound magnetic polarons. The ferromagnetism originates from ferromagnetism Corp which grow under Griffiths temperature TG , the adjacent bureau region of electron makes these ferromagnetism Corp polarize, and bound magnetic polarons is formed. While the temperature is lowered to TC the number and volume reach a crisis value, ferromagnetism of exchanging effect is occurred.