Improvement of tunneling magnetoresistance induced by antiferromagnetic spin orientation

Abstract

In magnetic tunnel junctions (MTJs), an antiferromagnetic iridium manganese (IrMn) layer neighboring a ferromagnetic electrode is indispensable for pinning the magnetization of the ferromagnet. The effect of its antiferromagnetism on adjacent ferromagnet and, thus, the quantum transport is, nevertheless, scarcely studied. Here, we investigate the role of antiferromagnetically orientated Mn spins in IrMn on the spin-dependent tunneling transport in IrMn/FeCo/MgO/FeCo/IrMn MTJ by analyzing the tunneling magnetoresistance (TMR) effect. The opposite spin orientation of Mn induces the mixing of Bloch symmetries, Δ1 and Δ5, irrespective of the spin alignment of the FeCo electrode. This auxiliary contribution from the Mn spins improves the tunneling in majority- and minority-spin channels in parallel configuration. In the antiparallel configuration, the tunneling in majority- and minority-spin channels is non-identical. The TMR as high as 8643% is obtained under equilibrium. In addition, the non-equilibrium behavior of TMR and the spin-filtering effect are examined in the voltage bias range of 10–50 mV. The TMR ratio of 3600% with the spin-filtering efficiency of ∼98% is maintained at 50 mV, presenting the MTJ as an effective spin-filtering device robust to the bias endurance. Finally, it is speculated that our device structure can be a potential spin–orbit torque-based MTJ that offers a giant TMR and promotes upscaling of the generation of multi-bit devices with a simplified design strategy.