Photoelectric properties of Mn-doped LiMgP new diluted magnetic semiconductor

Abstract

We optimized the geometry structures of Li1± y (Mg1− x Mn x )P for ( x =0.125; y =0, 0.125) by adopting the first-principles calculation of plane wave ultra-soft pseudo-potential technology based upon the density function theory (DFT). Then we calculated the electronic structures, formation energies, electric density difference and optical properties. The results reveal that spin polarization impurity bands were produced in Mn doped system. The properties of system and the orbits of participate in hybridization could be changed by dominating the amount of Li. The Mn doped system still revealed semiconductor properties, and the width of impurity band is 0.461 eV, and the magnetic moment is 4.98 μ в. The Li overdose system revealed metallicity, and the width of impurity bands increased to 0.890 eV, and the magnetic moment decreased to 4.10 μ в. Meanwhile the total energies and the formation energies reduced, the conductive capability increased. The Li deficient system revealed half metallicity, and the half-metallic band gap is 0.478 eV, and the magnetic moment is 4.02 μ в. Most of the charge overlap populations of LiMgP system are positive. It means all the chemical bonds of LiMgP are covalent bonds. Magnetism element Mn doped into the system creates Mn-P covalent bonds that are stronger than Mg-P bonds. In the Mn doped system, the quantity of share electron increased and the deviation of share electron decreased. The charge overlap population of Li-P bond is −0.02 which reveals ionic bonds. In the Li overdose system, the charge overlap population of Mn-P bonds reach the minimum value of 0.52. The density of states of Mn3 d and P3 p at the Fermi level is larger than that of single doped Mn, but at the same time, the interaction of the Mn-P bonds is weakened due to the participation of Li2 s in orbital hybridization. Formation energy and total energy become lower. And in the Li deficient system, the charge overlap population of Mn-P bonds reached the maximum value of 0.69, and the bonds lengths reached the minimum value. The electron cloud of Mn atoms and P atoms is the densest, and the deviation of the share electron is the weakest. The results reveal that p-d hybridization happened in Mn3 d and P3 p , and the hybridization was the strongest. The deficiency of the electron cloud of P atoms of charge density difference was caused by the deficiency of Li atoms. Analyzing images of optical properties can find that the imaginary part of dielectric function and the optical spectroscopy appeared a new peak at low energy region in Mn doped system. And the complex refractive index functions have a significant change at the same time. It means the system has an augment optical absorption range, and energy loss get lower.