Amplification of spin-transfer torque in magnetic tunnel junctions with an antiferromagnetic barrier

We theoretically study spin-transfer torques in magnetic tunnel junctions (MTJs) with an antiferromagnetic insulator (AFI) as the tunnel barrier. When a finite voltage bias is applied to the MTJ, the energy relaxation of the tunnel electrons leads to asymmetric heating of two metallic layers. Consequently, there would be a magnon current flowing across the AFI layer, resulting a magnon transfer torque in addition to the electron spin-transfer torque. Comparing to MTJs with a nonmagnetic insulator which prohibits the magnon transmission, we find the magnon transfer torque with an AFI barrier could be several times larger than the conventional spin-transfer torque of the tunnel electrons. This study presents a potential method to realize more efficient switching in MTJs and provides a motivation of experimental search for AFI-based MTJs.