Intrinsic ambient ferromagnetism in ZnO:Co induced by Eu codoping

We manipulate the interaction of Co's 3d and Eu's 4f electrons to design and fabricate ZnO: Co +Eu, which possesses intrinsic ferromagnetism at ambient temperature. The results show that the Eu ions tend to neighboring Co ions in order to eliminate the lattice distortion caused by the larger Eu ions via strain coupling. It was also revealed that the preference of parallel spin alignment between Eu and Co ions results in ferromagnetism. The theoretical analyses and our experimental results evidenced that the induced ferromagnetism in the Eu and Co codoped ZnO is intrinsic at ambient temperature. (C) 2011 American Institute of Physics. [doi:10.1063/1.3530840]