新型稀磁半导体Fe掺杂LiZnP的光电性质

采用基于密度泛函理论的第一性原理计算法研究了新型稀磁半导体Li_(1±)_y(Zn_(1-)_xFe_x)P (x=0, 0.0625;y=0, 0.0625)的电子结构、磁性及光学性质.结果表明,Fe的掺入使体系产生自旋极化杂质带,Fe的3d态与Li2s态,Zn4s态以及P3p态的态密度峰在费米能级处出现重叠,产生sp-d轨道杂化,此时体系净磁矩最大,材料表现出金属性,导电性增强.当Li空位时,导电性减弱,但杂质带宽度最大,居里温度最高.而Li填隙时,体系形成能最低,材料变为半金属性,表现为100%自旋注入,表明掺杂体系的磁性和电性可以分别通过Fe的掺入和Li的含量进行调控.对比光学性质发现,Li空位时,在介电函数虚部和复折射率函数的低能区出现新峰,扩大了对低频电磁波的吸收范围.能量损失函数表明掺杂体系具有明显的蓝移效应,且Li填隙时有更强的等离子共振频率.

Electronic structures and optical properties of Fe-doped LiZnP new diluted magnetic semiconductors

Using the first-principle density functional theory based on the full potential linearized augmented plane wave method, the geometric structures of new diluted magnetic semiconductor Li1±y(Zn1−xFex)P (x=0, 0.0625; y=0, 0.0625) were optimized. The electronic structures, half-metallic properties, formation energies and optical properties were calculated and discussed in details. The results show that the doping of Fe causes the system to produce a spin-polarized impurity band. The density of Fe 3d, Li 2s, Zn 4s and P 3p states overlaps at the Fermi level, leading to sp-d orbital hybridization. The system has the biggest magnetic moment and exhibits metallicity, its conductivity is enhanced. When Li is insufficient, the conductivity is weakened, but the impurity band width and the Curie temperature increases. While the excess of Li makes the formation energy reduce. The material becomes half-metallic and exhibits 100% spin injection. The magnetic and electrical properties of the doped system can be regulated by the incorporation of Fe and off-stoichiometry of Li respectively. Comparing optical properties indicate that the imaginary part of the dielectric function and complex refractive index function of Li insufficient system both have new peaks in the low energy region, which enhances the absorption of low frequency electromagnetic waves. The energy loss functions of the doped systems show obvious blue-shift, and the oscillating range of plasma becomes wider in Li excess compounds.