Role of nitrogen-related complex in stabilizing ferromagnetic ordering in a rare-earth and nitrogen codoped ZnO

We report the ferromagnetic enhancement in a rare-earth and nitrogen co-doped ZnO thin film. To reveal the origin of ferromagnetism, we perform a comparative study on undoped, Nd-doped, N-doped and (Nd, N)-codoped ZnO thin films by combining experiments with first-principles calculations. Compared with the Nd-doped ZnO, the N incorporation into the Nd-doped ZnO to form 2NdZn-NO complex leads to the more stable ferromagnetic coupling between two Nd atoms, which is well supported by first-principles calculations. Our results suggest that the electronic structure alteration via codoping engineering plays a critical role in stabilizing the ferromagnetic orderings.