Toggle spin-orbit torque (SOT)-driven magnetoresistive random access memory (MRAM) with perpendicular anisotropy has a simple material stack and is more robust than directional SOT-MRAM. However, a read-before-write operation is required to use the toggle SOT-MRAM for directional switching, which threatens to increase the write delay. To resolve these issues, we propose a high-speed memory architecture for toggle SOT-MRAM that includes a minimum-sized bit cell and a custom read-write driver. The proposed driver induces an analog self-terminating SOT current that functions via an analog feedback mechanism that can read and write the toggle SOT-MRAM bit cell within a single clock cycle. As the read and write operations are completed within 570 ps, this memory architecture provides the first viable solution for nonvolatile L3 cache.

Resistance-based memory devices are considered as a strong candidate for next-generation nonvolatile memories as well as potential application in high density embedded cache. These devices can be programmed to different resistance states by applying electrical bias. Read operation then senses the programmed state by discharging a shared data line through the memory cell. However, as the dimensions of the device scale down, its resistance increases and the distribution widens, which leads to reduced sensing margins and degradation in read performance. In the proposed dual-data line (DDL) read scheme, we recycle current flowing through the memory cell during the read operation to create an additional voltage swing on a secondary data line, and combine it with the signal on the original data line to reduce sensing time and energy. Performance comparison with the conventional read scheme is derived theoretically by using circuit analysis and verified through simulation on an array critical path constructed in 65-nm technology. Results show that the DDL scheme can improve sensing margins by an average of 86%, which translates to a sensing time reduction of 47%, across various device conditions. For the same read performance, the sensing energy is decreased by 48%.

In this paper, we propose a non-volatile stochastic computing (SC) scheme using voltage-controlled magnetic tunnel junction (VC-MTJ) and negative differential resistance (NDR). The proposed design includes a VC-MTJ based true stochastic bit stream generator and VC-MTJ and NDR based stochastic adder, multiplier, register, which are experimentally demonstrated using 60nm VC-MTJ and CMOS NDR connected on die. These components are then used to realize FIR filter and AdaBoost (machine-learning algorithm). 3X–37X energy advantage is shown for the proposed SC compared with CMOS binary arithmetic ASIC and SC designs.

A word line pulse (WLP) circuit scheme is proposed toward the implementation of magnetoelectric random access memory (MeRAM). The circuit improves the write error rate (WER) and cell area efficiency by generating a better write pulse compared to conventional bitline pulse (BLP) techniques in terms of the pulse slew rate and amplitude. For the voltage-controlled magnetic anisotropy-induced precessional switching of the magnetic tunnel junction (MTJ), the write pulse shape has a large impact on the switching probability. Typically, a square shape pulse results in higher switching probability compared to that of a triangular shape pulse with long rise and falling edges, since the square shape pulse causes a more stable precessional trajectory of the free layer magnetization by providing a relatively constant in-plane-dominant effective field. Compared to the BLP scheme, the WLP can generate a better square shape pulse by eliminating discharge paths under the pulse condition, using the gain of the access transistor, and effectively diminishing the capacitive loading which needs to be driven. A macrospin compact model of voltage-controlled MTJ shows that the WLP can improve WER by${10}^{7}$times and allow MeRAM to have four-time improvement in area efficiency of driver circuits compared to the BLP.

Spin-transfer torque random access memory (STT-RAM) and magnetoelectric random access memory (MeRAM) are promising non-volatile memory technologies. But STT-RAM and Me RAM both suffer from high write error rate due to thermal fluctuation of magnetization. Temperature and wafer-level process variation significantly exacerbate these problems. In this paper, we propose a design that adaptively selects optimized write pulse for STT-RAM and MeRAM to overcome ambient process and temperature variation. To enable the adaptive write, we design specific MTJ-based variation monitor, which precisely senses process and temperature variation. The monitor is over 10X faster, 5X more energy-efficient, and 20X smaller compared with conventional thermal monitors of similar accuracy. With adaptive write, the write latency of STT-RAM and MeRAM cache are reduced by up to 17% and 59% respectively, and application run time is improved by up to 41%.

A non-volatile spintronic programmable logic (SPL), based on a 3-teriminal magnetic tunnel junction (MTJ), is presented and simulated using a compact device model. The SPL structure is compatible with CMOS technology and can be fabricated in the back end of line (BEOL). The proposed SPL exploits the gate-voltage-modulated spin Hall effect (V-SHE) switching, which combines the voltage controlled magnetic anisotropy (VCMA) effect and SHE, as a parallel configuration method. The VCMA modulates the coercivity of the MTJ, reducing the critical current for the SHE to change the state of MTJs. This allows the SPL to achieve 100x faster configuration speed due to the parallel configuration, and 32% area reduction because of minimized transistors in the write circuit, compared to conventional spin transfer torque memory (STT-RAM) based programmable logic.

Spintronics is regarded as a promising solution for resolving the major challenging issues related to the scaling of Si-based complementary metal–oxide–semiconductor (CMOS) technology as it offers the advantages of combing the spin and charge degrees of freedom. After decades of progress, the quintessence to achieve practical low-dissipation applications lies in the ability to manipulate magnetic states by electric field via several different physical mechanisms. Among them, the emergence of the spin-orbit coupling engineering has been shown to dramatically reduce energy dissipation and improve the performance as well as to multiply spintronic device possibilities and functionalities for a new generation of ultralow-power nonvolatile spintronic systems. This article provides a review of the current development including fundamental physics and experimental implementations of electric-field-controlled ferromagnetism in dilute magnetic semiconductors, voltage control of magnetic anisotropy, spin-orbit-torque-assisted magnetization switching, and antiferromagnetic (AFM) material-based spin-orbitronic systems. We provide an assessment in terms of scaling of energy, speed, and size. Finally, we offer an outlook of electric-field-controlled spintronic applications, particularly in view of their integration with CMOS to form hybrid spintronic circuits.