First-Principles Study of Spin Transport in CrO2–Graphene–CrO2 Magnetic Tunnel Junction

We investigate the spin-dependent electronic transport properties of magnetic tunnel junction (MTJ) consisting of graphene nanosheet sandwiched between two CrO2 half-metallic ferromagnetic (HMF) electrodes. I–V characteristics for both parallel and antiparallel magnetization states of the junction are calculated. A large value of tunnel magnetoresistance (TMR) and perfect spin filtration was obtained using HMF electrodes as compared to ferromagnetic electrodes reported in past, which suggest half-metallic ferromagnetic electrodes as a suitable candidate over ferromagnetic electrodes for implementing graphene sheet-based MTJs. A high value (∼89 %) of tunnel magnetoresistance is obtained at zero bias voltage, which reduces to ∼68 % at a bias voltage of 0.2 V and increases as the bias voltage is increased from 0.4 to 0.6 V. At higher bias voltages in the range of 0.8 to 1.2 V, the TMR does not change much and remains high at ∼88 %. The high value of TMR suggests its usefulness in spin valves and other spintronics-based applications. The spin-dependent non-equilibrium transport is also investigated by analyzing the bias-dependent transmission coefficients.