新型稀磁半导体Mn掺杂LiMgAs的光电性质

基于密度泛函理论第一性质原理平面波超软赝势法,对理想新型稀磁半导体Li1±y(Mg1-xMnx)As (x=0,0.125;y=0,0.125)进行几何结构优化,计算并分析了体系的电子结构、磁性和光学性质。结果表明,掺杂体系的磁性和电性可以分别通过Mn的掺入和Li计量数的调控来改变,掺Mn后形成Mn-As极性共价键,且引入与Mn有关的自旋极化杂质带,体系为半导体磁性材料。Li不足时,p-d杂化使体系变为半金属性,表现为100%的自旋注入,Mn-As键的重叠电荷布局最大,键长最短。而Li过量时,sp-d杂化则使体系变为金属性,居里温度最高,形成能最低,导电能力最强。对比光学性质发现,Li不足和过量时,介电函数和光吸收谱在低能区出现新峰,增强了体系对低频电磁波的吸收。掺杂体系的能量损失峰均向高能方向偏移,呈现明显的蓝移特征,且峰值急剧减小,表明其等离子共振频率显著降低,而Li过量的等离子振荡范围最宽。

Photoelectric properties of Mn-doped LiMgAs new diluted magnetic semiconductors

Using the first-principle density functional theory based on the full potential linearized augmented plane wave method, ideal new diluted magnetic semiconductor Li1±y(Mg1-xMnx)As(x=0, 0.125;y=0,0.125) were geometrically optimized and calculated. The electronic structures and optical properties were calculated and discussed in detail. The results show that the magnetic and electrical properties of the doped system could be separately regulated by Mn doping and Li off-stoichiometry. Mn-doped LiMgAs made the system form Mn-As polar covalent bond. The system had spin polarization impurity bands relevant with Mn and presented semiconductor magnetic material. In the Li deficient system, p-d hybridization led to the system exhibit half metallicity and 100% spin injection. The Mn-As bond had the largest charge overlap population and the smallest bond length. While sp-d hybridization made Li overdose system become metallicity. The Curie temperature was the highest, the formation energy was the lowest, and the electrical conductivity was greatly enhanced. Comparing optical properties indicated that when the dielectric function and optical absorption spectrum both had new peaks appear in the low energy region for the Li excess and insufficient compounds, and the absorption of the low-frequency electromagnetic wave increased. The energy loss spectrum peaks of the doped system were all shifted to the high-energy region, showing obvious blue shift phenomenon. Meanwhile, the peaks were all greatly reduced, indicating that the plasma resonance frequency of the doped system decreased significantly. The oscillating range of plasma was the widest in Li excess compounds.