Parameter variation investigation of Magnetic Tunnel Junctions

Magnetic Tunnel Junction (MTJ) is a widely used spintronics structure in many applications. The tunneling magneto-resistance (TMR) is an important metric indicating MTJ sensitivity, and modeling this phenomenon is nontrivial, owing to the complicated nature of spin dependent tunneling. Deploying numerical tools such as OOMMF and SpinFlow3D software, which treats tunneling by way of a voltage-dependent areal conductance, we study properties of MTJs, such as TMR, varying a number of parameters, including MTJ stack taper angle, parameters of voltage-dependent areal conductance associated with the MgO barrier, and other parameters accessible in the model, including bias and coercive field behavior based on geometrical parameters. We find that a taper angle, which is a consequence of fabrication processes, has negligible effect on TMR. Additionally, it is shown that the current distributions in MTJs, when a bias voltage is applied, is actually nonuniform. We also show that introducing geometrical artifacts in the structure can strongly influence properties such as coercive and bias fields in MTJs.