Abstract. Using first-principles calculations based on density functional theory, we investigated systematically the electronic structures and magnetic properties of Ti monodoping and (Ti, Mg vacancy) codoping in MgO. The results indicate that a single Ti substitution of Mg prefers the ferromagnetic ground state and behaves a metallic character. In addition, it has been found that the two Ti dopants favor AFM coupling in the near configuration, whereas the FM state is more stable in the far configuration. Interestingly, the FM stability can be evidently intensified by introducing Mg vacancy. The magnetic moment mainly comes from the spin polarized Ti 3d and O 2p electrons which can be explained in terms of p-d hybridization mechanism and room temperature ferromagnetism can be expected. Furthermore, the doped Ti atoms in the MgO host have no clustering tendency. These results suggest that the Ti-doped MgO is a promising candidate material for room temperature spintronics applications.
IntroductionDiluted magnetic semiconductors (DMSs) have attracted considerable attention because they hold the promise of using electron spin, in addition to its charge, in creating a new class of spintronic semiconductor devices that combine the function of information processing and storage [1] [7]. Much effort has been devoted to study the nature of ferromagnetism, aiming at designing ferromagnetic DMS materials with RT ferromagnetism. However, a number of studies indicate that the RT ferromagnetism may come from precipitation of magnetic clusters or from the secondary magnetic phases and no convincing evidence can verify that the observed ferromagnetism is intrinsic. These extrinsic magnetic behaviors are undesirable for practical application. Up to now, the origin of ferromagnetism in oxide DMSs is still unclear.Recently, a new class of oxide ferromagnets has arisen, bringing new challenges for the understanding of the underlying physics of long-range ferromagnetic ordering in oxide compounds [8][9][10][11][12][13][14][15][16][17]. In these systems, the ferromagnetic behavior is driven by native defects and therefore there are no complications arising from additional phases or clustering effects induced by the doping process, thus they are considered as promising spintronic materials. However, the origin of the magnetism remains to be clarified.MgO has recently attracted a great deal of attention as a promising material to understand the magnetic mechanism of oxide ferromagnets. If MgO is made ferromagnetic via dilute magnetic doping, it may also work as a spin filter or induce a large magnetic-field effect. Besides that, Mg is an