Joseph S. Friedman


Toggle Spin-Orbit Torque (SOT) Magnetoresistive Random-Access Memory (MRAM) with Perpendicular Magnetic Anisotropy (PMA)

Magnetoresistive random-access memory (MRAM) promises non-volatility with SRAM-like speed and DRAM-like density and energy-efficiency. However, the efficient spin-orbit torque (SOT) switching of MRAM with perpendicular magnetic anisotropy (PMA) requires complex structures with poor tolerance of noise. To resolve this issue, toggle SOT MRAM with PMA enables robust switching with a simple device structure.

Toggle Switching Mechanism

As illustrated in the animation below, each current pulse through the heavy metal applies SOT to toggle the magnetization of the free magnetic layer between the up (1) and down (0) memory states. (As both magnetic latyers have PMA, the stable magnetization states are along the vertical easy axis.) When the magnetizations of the free and fixed layers are in the parallel orientation (both down), the resistance across the tunnel barrier is low; when these magnetizations are anti-parallel, the resistance is high. The SOT current pulse is used to write to this memory device, while applying a voltage across the magnetic tunnel junction enables reading of the resistance state.

Directional Switching with Toggle MRAM

To write a particular value (1 or 0) to this toggle MRAM device, simple logic must be added to determine whether a toggle switching pulse should be applied. As shown in the figure and truth table below, directional switching can be achieved with an XOR between the input data (D) and the data present in the MRAM (Q). If D = Q, then no toggle pulse need be applied (T = 0); if D ≠ Q, a toggle pulse is required to switch the MRAM state (T = 1).

Related Publications

  1. N. Hassan, F. Garcia-Sanchez, S. P. Lainez-Garcia, P. Khalili Amiri, J. S. Friedman, Field-Free Toggle Spin-Orbit Torque MRAM with Perpendicular Magnetic Anisotropy, The Magnetic Recording Conference, Aug. 2020.
  2. N. Hassan, S. P. Lainez-Garcia, F. Garcia-Sanchez, J. S. Friedman, Spin-Orbit Torque Driven Toggle Mode MRAM with Perpendicular Magnetic Anisotropy, SPIE Spintronics, Aug. 2020 (invited).
  3. N. Hassan, S. P. Lainez-Garcia, F. Garcia-Sanchez, J. S. Friedman, Toggle Mode Spin-Orbit Torque Driven Perpendicular Magnetic Anisotropy MRAM, Conference on Magnetism and Magnetic Materials, Nov. 2019.
  4. N. Hassan, S. P. Lainez-Garcia, F. Garcia-Sanchez, J. S. Friedman, Toggle Spin-Orbit Torque MRAM with Perpendicular Magnetic Anisotropy, IEEE Journal on Exploratory Solid-State Computational Devices and Circuits 5:2, 166-172 (2019).