Tunneling magnetoresistance enhancement by symmetrization in spin-orbit torque magnetic tunnel junction

Heavy metals with strong spin-orbit coupling (SOC) have been employed to generate spin current to control the magnetization dynamics by spin-orbit torque (SOT). Magnetic tunnel junction based on SOT (SOT-MTJ) is a promising application with efficient writing operation. Unfortunately, SOT-MTJ faces the low tunneling magnetoresistance (TMR) problem. In this work, we present an ab initio calculation on the TMR in SOT-MTJ. It is demonstrated that TMR would be enhanced by SOT-MTJ symmetry structure. The symmetrization induces interfacial resonant states (IRSs). When IRSs match identical resonances at the opposite barrier interface, resonant tunneling occurs in SOT-MTJ, which significantly contributes to the conductance in parallel configuration and improves TMR. We demonstrate the occurrence of resonant tunneling by transmission spectra, density of scattering states and differential density of states. We also point out that the thickness of heavy metal has limited influence on TMR. This work would benefit the TMR optimization in SOT-MTJ, as well as the SOT spintronics device.