Fully Nonvolatile and Low Power Full Adder Based on Spin Transfer Torque Magnetic Tunnel Junction With Spin-Hall Effect Assistance

Abstract

As technology node scales down below 90 nm, the conventional complementary metal oxide semiconductor (CMOS) logic circuits suffer from various problems such as high standby power due to increase in leakage current. Spintronic devices based on magnetic tunnel junction (MTJ) is one of the most promising technology candidates for the future of the digital circuits. MTJ-based logic circuits can offer nonvolatility, high endurance, high density, low standby power dissipation, and 3-D integration capability with the CMOS technology. In recent years, several full-adder circuits are proposed based on MTJs that are not fully nonvolatile since they use MTJs to store only one of their inputs. This paper proposes a fully nonvolatile magnetic full-adder (MFA) circuit offering the capability of power gating with no loss of data. The proposed circuit stores all the inputs in MTJs using the spin-transfer torque (STT) method assisted by the spin-Hall effect (SHE). Thanks to the SHE assistance, delay and power consumption of the MTJ switching are reduced significantly. Moreover, as a result of lower write current, the endurance of the oxide barrier can be increased. Using a three-terminal SHE–STT–MTJ model and a 45 nm CMOS SPICE model, we simulated and validated the functionality of our design and compared it with some recent previous MFAs. Simulation results reveal that the proposed MFA offers considerable superiorities over the recent counterparts.