On the origin of the ferromagnetism in Zn0.8Mn0.2O having a higher Curie temperature than Zn0.8Co0.2O

Zn0.8Co0.2O and Zn0.8Mn0.2O films were deposited on substrates by a sol–gel technique. X-ray diffraction, field-emission scanning electron microscopy, photoluminescence, and ferromagnetism measurements were used to characterize these dilute magnetic semiconductors. It is shown that the ferromagnetic properties might be related to the formation of acceptor-like defects in the Zn0.8Co0.2O and Zn0.8Mn0.2O films. It is found that ferromagnetic Zn0.8Mn0.2O has a higher Curie temperature than Zn0.8Co0.2O. In addition, the higher ratio of grain-boundary area to grain volume of Zn0.8Mn0.2O than Zn0.8Co0.2O indicates that grain boundaries and related acceptors are the intrinsic origin for ferromagnetism.