**3. Results and discussion**

Recently, a lot of research work has been reported on RE ion-based DMS ZnO [36]. Sun et al. [37] reported La-doped ZnO quantum dots in which luminescent behavior is greatly enhanced by introducing defects and oxygen vacancies (VO). This is due to larger ionic size of La3+ in ZnO lattice that induces stress. However, Bantounas et al. [38] suggested the weak magnetic coupling in Gd/ZnO and the material remain paramagnetic at room temperature. Aravindh et al. [39] gives origin of ferromagnetism in Gd/ZnO in which oxygen vacancies play an important role. Using DFT calculation, it is analyzed that the RE Ce atoms replaced those Zn sites in the wurtzite structure, which is the nearest neighbor to TM/Fe or Co atoms [40]. The 4f electrons in Ce are tightly bound around the nucleus and shielded by 5s2 p6 d1 6s<sup>2</sup> electrons, leading to strong local spin. For Ce-doped TM/ZnO, the larger ratio of dopant cation to cation radius structure causes more defects, leading to a larger concentration of electrons and holes.

#### **3.1 Wurtzite structure and defect calculation in DMS ZnO**
