Defect-mediated ferromagnetism in ZnO:Mn nanorods

Abstract

In this work, the structural, chemical and magnetic properties of ZnO:Mn nanorods were investigated. Firstly, well-aligned ZnO nanorods with their long axis parallel to the crystalline c-axis were successfully grown by the vapor phase transport technique on Si substrates coated with a ZnO buffer layer. Mn metal was then diffused into these nanorods at different temperatures in vacuum. From SEM results, ZnO:Mn nanorods were observed to have diameters of ~100 nm and lengths of 4 µm. XPS analysis showed that the Mn dopant substituted into the ZnO matrix with a valence state of +2. Magnetic measurements performed at room temperature revealed that undoped ZnO nanorods exhibit ferromagnetic behavior which may be related to oxygen vacancy defect-mediated d 0 ferromagnetism. ZnO:Mn samples were seen to show an excess room temperature ferromagnetism that is attributed to the presence of oxygen vacancy defects forming bound magnetic polarons involving Mn.

Room temperature ferromagnetism in magnetron sputtering prepared Mn-doped ZnO thin films

“…Therefore, a great density of native defects in conjunction with Mn doping helps to produce more BMPs which yields a greater overall volume occupied by BMPs, leading to the overlap of BMPs, resulting in ferromagnetism. 5) Some groups' results well agree with BMP model, they found that the ferromagnetism of their samples became stronger with the increase of the concentration of V o 19,[29][30][31] and the Mn nearest neighbour short range exchange interaction (ferromagnetic=antiferromagnetic) is strongly dependent on the concentration of structural defects. 19,32) Since in our study, the result shows that the sample which gets minimum V o concentration is found to be stronger ferromagnetism, the BMP model is not fitted.…”