MRAM_ex03.in : Magnetic Switching in an SOT MRAM Device

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MRAM_ex03.in : Magnetic Switching in an SOT MRAM Device

Every software package contains a full set of examples suitable for that version and are installed with the software. If you see examples here that are not in your installation you should consider updating to a later version of the software. These examples can be used by beginners and advanced users for product evaluation, teaching purposes, and self-training.

Required Modules

Victory Mesh

3D Meshing
3D Solid Modeling

Victory Device

3D Simulator
3D MRAM

This example shows the transient behavior of an SOT MRAM device that is switched using an STT assist. The input deck consists of two parts that demonstrate how to:
-) Create and refine a mesh for the SOT MRAM structure using Victory Mesh.
-) Perform a switching simulation and depict the simulation results using Victory Device.

In the first section, Victory Mesh is started by the command “GO VICTORYMESH “. The CUBOID statement is used to create the heavy metal layer at the bottom of the structure and the LAYERS statement is used to generate the SOT pillar structure with an ellipsoidal base. The two complexes are joined, resulting in the SOT MRAM structure. At next, this structure is remeshed using a Delaunay mesh, refined around the free layers, and saved in a structure file.

The micromagnetic simulation is started with the simulation flag “-mram “. The MESH statement requires the flags ENABLE.SOT, ENABLE.SOT.BCS, and ENABLE.INT.SOC for considering the SOT effect (magnetoelectronic circuit model, the Rashba Edelstein effect). Next, the electrodes are defined on the ELECTRODE statemetns and the SOT interface between the free layer and the heavy metal is set usig the INTERFACE statement. Then, the parameters in the Landau-Lifshitz-Gilbert equation (the Gilbert damping factor, the saturation magnetization, the exchange constant, and the anisotropy energy) are specified for the free and the reference layer on the LLGE statement.

The SOT command is applied to define the parameters for the Spin-Hall effect and the SOT interface models. The parameter SPIN.HALL.LAYER identifies the heavy metal layer and the parameter SPIN.HALL.ANGLE is used the additional SHE term in the Spin-Drift-Diffusion equation. The spin mixing parameters (SPIN.MIXING.CONDUCTANCE.REAL, SPIN.MIXING.CONDUCTANCE.IMAG) define the spin scattering at the SOT interface according to the magnetoelectronic circuit model. The Rashba Edelstein effect is specified by the potentials SPIN.DEPENDENT.POTENTIAL, EXCHANGE.POTENTIAL, and RASHBA.POTENTIAL along with the parameters FERMI.WAVE.VECTOR, RELAXATION.TIME.NM, and the RELAXATION.TIME.FM.

The parameters in the Spin-Drift-Diffusion equation are set on the SDDE statement. They include the resistance in the parallel and the anti-parallel configuration and a number of region-dependent parameters, such as electron diffusivity, the resistivity, and the in-plane and out-of-plane polarization parameters.

The magnetic orientations of the free and the reference layers are initialized on the LOAD statement.

The PROBE command is applied to select the logged quantities, ie. the magnetization and the spin accumulation in the free layer. As specified on the OUTPUT statement, their distributions are also saved in the structure files.

In the following SOLVE statement, the STT assist is realized by a short bias pulse, defined by a piecewise linear potential on the contact with index 2.

The plotted spin accumulation shows a strong increase in its y-component during the STT pulse. This spin accumulation results in a successful switching, visible in the time evolution of the free-layer magnetization and the two snapshots of the magnetization in the z-direction.