Extremely Low Switching Current STT-MRAM Device With Double Spin Transfer Torque

In this work, we demonstrate an STT-MRAM device with double reference layer that shows extremely low critical switching current density. A synthetic antiferromagnetic (SAF) layer [Co/Pt]n/Ru/[Co/Pt]m is used as the upper reference layer in the STT-MTJ device with perpendicular magnetic anisotropy (PMA) which can apply extra spin transfer torque to the free layer in the process of data writing. The ac R-I experimental results show that when the magnetization directions of upper and nether reference layer are antiparallel state, the JC is only 1.230 MA/cm2 for AP2P and 1.867 MA/cm2 for P2AP, when the pulse width is 10ns, which is more than $5\times $ lower than the classical single reference layer STT-MTJ device with the close thermal stability. Our work provides a new way to achieve the ultra-low power STT-MRAM for IoT application.