Tunnelling magnetoresistance and spin filtration effect in functionalized graphene sheet with CrO2 as electrode: An ab-initio study

Abstract

Spin-dependent transport behavior of functionalized graphene sheet with CrO2 as half-metallic magnet (HMM) electrodes are explored using DFT (density functional theory) in a combination with non-equilibrium Green’s function formalism (NEGF). Functionalized graphene sheet with Hydrogen and Fluorine atoms are examined as ultra-thin tunnel barriers in the magnetic tunnel junction devices. Computations based on the DFT for functionalization of graphene sheet with H and F atoms show opening of the band gap in the graphene sheet. A band gap opening of 3.53 eV, 3.16 eV, and 2.64 eV have been observed when Graphene sheet is functionalized with H atoms on both sides, F atoms on both sides, and both F and H atoms on each side of the graphene sheet respectively. The results of all the three functionalized graphene sheet configurations have been compared. On comparison of the results for the three configurations, it is observed that a large value of tunneling magnetoresistance (TMR) around 344 × 103% is obtained for the H-Graphene-F device configuration. This suggests that the H-Graphene-F device configuration acts as a perfect ultra-thin insulating barrier for the spin-based devices. Negative differential resistance (NDR) behavior have been observed for F-Graphene-F and H-Graphene-F device configurations in parallel magnetization (PM) case. All the three configurations show perfect spin filtration efficiency of around 100%. Applied voltage dependent transmission spectrum have been plotted for all the three device configurations to validate the current-voltage behaviour. These unique and interesting nature of all the three devices suggest their applications in spintronics domain.