Non-volatile logic & memory based on STT-MTJ and SOT-MTJ devices
Loy, Desmond Jia Jun
Date of Issue2016-05-04
School of Physical and Mathematical Sciences
With traditional complementary metal oxide semiconductor (CMOS)-based devices and switching methods facing the limits of scalability and read/write efficiency, alternative methods of switching needs to be investigated. In this work, two current-driven switching methods, spin transfer torque (STT) and spin orbit torque (SOT) switching were investigated. In addition, various designs of magnetic tunnel junctions (MTJs) as well as their logic operations were analysed. A Symmetrical (Sym) STT-MTJ design was first investigated. This novel STT-MTJ design has 4-terminals and has its read and write paths separated. This greatly enhances the reliability of the read/write operations of the MTJ. The switching process was assisted by STT-domain wall motion (DMW) and by analysing the current flow throughout the circuit, “universal” logic gates (NAND, AND, NOR and OR) could also be obtained from various circuit configurations of this Sym STT-MTJ. SOT-MTJs are more suitable for logic operations due to its ability to isolate its read and write paths as well as other properties such as better energy efficiency and smaller write current as compared to STT-switching. In continuation of this work, SOT-MTJ based spin logic architectures using SPICE were proposed and demonstrated while a half-adder and a flip-flop SR latch logic structure constructed using SOT-MTJs in a circuit configuration were analysed.
Final Year Project (FYP)