Large magnetoresistance and spin-polarized photocurrent in Mn2.25Co0.75Ga0.5Sn0.5/MgO/Mn2.25Co0.75Ga0.5Sn0.5 magnetic tunnel junctions

Abstract

With the development of information storage devices with high density, low power consumption and multi-means regulation, magnetic tunnel junctions (MTJs) with completely spin polarized materials as electrodes have attracted much attention. Heusler alloy Mn2.25Co0.75Ga0.5Sn0.5(MCGS) is a recently fabricated spin gapless semiconductor with 100 % spin polarization and high Curie temperature of 725 K. Here, the spin-dependent electronic transport and photoelectric properties of MCGS/MgO/MCGS MTJs are investigated systematically by density functional theory and non-equilibrium Green's function method. It is found that the MCGS/MgO/MCGS MTJs with four different terminations all present high tunnel magnetoresistance (TMR) and the maximum TMR is up to 6.51 × 106 %. The TMR value can be reduced and switched between positive and negative values by applying bias voltage, which can be used to designed magnetic logic devices. Furthermore, perfect spin injection efficiency can be obtained in the MCGS/MgO/MCGS MTJs and the switch of the spin channel can be controlled by the magnetization configuration of the ferromagnetic electrodes. Moreover, nearly 100 % spin-polarized photocurrent can be obtained by tailoring the polarization angle and photon energy of polarized light. The linearly polarized light is more favorable than circularly polarized light to generate high spin-polarized photocurrent. These results provide a theoretical guidance for designing the spin and optical tunable spintronic devices.