First-principle study on the electronic and magnetic properties of conducting materials

Abstract

Density-functional theory (DFT) method with periodic boundary consition is used to compute the total energy, ferromagnetic moment atomic charge of conducting system. We use localized pseudopotentials to integrate away core energy levels and very flexible basis set ade up of numerical atomic-like wave functions to handle valence electrons. The use of minimal bases allow for fast calculations which already provide a qualitative understanding of the simulated material. Accurate calculations can be performed at a higher numerical cost, using more complete basis set. Assessment of the degree of reliability of a basis set might be essential, since competing would-be ground states may in some instances have small energy differences. We can calculate a system consist of hundreds of atoms accurately by using pseudopotential and atomic-like wave functions. Focusing on the framework of how to realize the molecular spintronics in a single molecular magnet, we present theoretical studies on the spin-polarized quantum transport behavior through a single $Mn_{12}$ molecular magnet. Out theoretical results were obtained by carrying out DFT calculation with the Keldysh nonequilibrium Green function formalism. The ultimate goal of the molecular spintronics is to develop single molecule transistors which generate spin-polarized currents through the molecular magnet. We obtained the density of states, the transmission coefficients and the characteristic features of the current-voltage (I-V) on the spin-polarized transport properties of $Mn_{12}$ by the theoretical calculation. These results show the possibility for the realization of molecular spintronics using single molecular magnets. Using a nonequilibrium density functional calculation, we investigated the electronic transport properties and fundamental mechanism of spin polarization as a function of the location of impurities from the center to an edge of a graphene nanoribbon device(GND) with zigzag edges. A center-located ...