Theoretical Studies On The Structures And Magnetic Properties Of Cr_1-2@Ga₁₂N₁₂ And Mn_1-2@Zn₁₂Te₁₂ Clusters

Diluted magnetic semiconductors?DMS? show a very broad application prospects in the field of spintronics because of their wide energy band gap, magnetic, photoelectric property, semiconducting properties and so on. Therefore, magnetic semiconductor materials have become the further research subjects no matter from the basic science research and the potential applications.Recently, a lot of meaningful explorations have been studied both by experimental and theoretical workers. For example, GaN and ZnTe are the archetypical DMS system with band gap of 3.4 e V and 2.26 e V. Among the systems, TM doped GaN, ZnTe DMSs have been prepared out in experiment, which show the ferromagnetic properties of room temperature. But, we still needs further theoretical calculation to reveal the magnetism regime in order to obtain their magnetic mechanism and eventually promote TM doped GaN, ZnTe DMSs apply in spintronics.In view of the above research background, the current magnetic theories research works about doped GaN and ZnTe clusters are mainly focused on the bulk and nanowires. Clusters as the important bridge connecting the small molecules and materials. Cluster usually displays some unique physical and chemical properties due to its size and quantum effect, the TM doped pure semiconductor clusters have been extensively attention. Considering the Ga₁₂N₁₂ and Zn₁₂Te₁₂ clusters are the specially stable structure, so, we study the structural, magnetic properties of Cr doped Ga₁₂N₁₂ clusters and Mn doped Zn₁₂Te₁₂ clusters, then to better reveal their magnetism mechanism. And eventually better promote the TM doped Ga₁₂N₁₂, Zn₁₂Te₁₂ clusters application in the spintronics. The main contents and results are as follows:1. Structural, electronic, and magnetic properties of Cr-doped Ga₁₂N₁₂ ClustersThe structural, electronic and magnetic properties of one or two Cr atoms doped Ga₁₂N₁₂ clusters have been systematically studied by means of density functional theory with generalized gradient approximation. The substitutional, exohedral, and endohedral doping are taken into account. For monodoped case, the exohedral isomers are found to be most favorable in energy and possessing 4?B total magnetic moment. For the bidoped clusters, the exohedral isomers are also found to be most favorable in energy, and antiferromagnetic?AFM? state is degenerate with the ferromagnetic?FM? state at larger Cr–Cr distance?>5??. In addition, the Cr–Cr direct interaction is more dominant than the FM interaction between two Cr atoms via N atom due to strong p–d hybridization in governing the two Cr atoms magnetic coupling, resulting in the bidoped clusters all favor the AFM state. The endohedral bidoped isomer is found to be a stable local minimum, and the direct Cr–Cr interaction causes the reduction of local magnetic moment of Cr to about 2?B.2. Structural, electronic, and magnetic properties of Cr-doped Ga₁₂N₁₂ ClustersThe structural, electronic and magnetic properties of one or two Mn atoms doped Zn₁₂Te₁₂ clusters have been systematically studied by means of density functional theory. According to the three different models viz. substitutional, exohedral, and endohedral doped clusters, we have been taken into account the possible configurations as much as possible. For monodoped case, the substitutional isomers are found to be most favorable in energy and possessing 5?B total magnetic moment. For the bidoped clusters, the FM state of endohedral doped clusters are found to be most favorable. The calculations show that the total magnetic moment of Mn doped Zn₁₂Te₁₂ clusters come mainly from Mn-3d, the Mn-4s and Mn-4p orbital also have some contributions. Due to the hybridization interaction, a small magnetic moment is also induced nearest neighboring Zn atoms and Te atoms. In addition, for substitutional and exohedral bidoped clusters, the Mn-Mn direct interaction is more dominant than the FM interaction between two Mn atoms via Te atom due to strong p–d hybridization in governing the two Mn atoms magnetic coupling. But, the the FM interaction between two Mn atoms via Te atom due to strong p–d hybridization is more dominant in the endohedral bidoped Zn₁₂Te₁₂ clusters. The clusters favor ferromagnetic state, which will has potential applications value in the functional applications of the nanoscale quantum devices.