Ultra-energy-efficient CMOS/magnetic nonvolatile flip-flop based on spin-orbit torque device

The spin-orbit-torque magnetic tunnel junction (SOT-MTJ) is a promising device for data storage. Most of the issues encountered with scalable spin transfer-torque (STT) devices are visibly moved. Thanks to a three-terminal architecture, the reliability is increased by separating the read and the write paths. Furthermore, SOT-induced magnetisation switching can be very fast, thanks to a low-resistive writing path. The writing operation is symmetrical. Thus, it requires the same current density to switch between the parallel and antiparallel states. All these advantages make the SOT-MTJ device an ultimate candidate for introducing non-volatility in ultra-fast and power-efficient integrated circuits. A mixed CMOS/magnetic non-volatile flip-flop (NVFF) is described. The proposed architecture offers the possibility to use the usual CMOS flip-flop functionality with possible magnetic data store and restore operations while keeping non-volatility when the circuit is powered off. With a 135 nm dimension, the SOT-MTJ-based NVFF demonstrated a very high switching with a 5× decrease in terms of writing energy/bit when compared with an STT device.