A Compact XOR Gate Implemented With a Single Straintronic Magnetic Tunnel Junction

The xor Boolean logic gate is widely used in many applications such as encryption (xor ciphers), binary addition (half- and full-adders), error detection (parity bits), etc., but is challenging to construct because of its demanding conditional dynamics. It typically requires multiple logic switches or other types of gates, which results in a large gate footprint and low logic density. Here, we present the design of an xor gate with a single straintronic magnetic tunnel junction (MTJ) which reduces the footprint dramatically. Such a gate is nonvolatile and hence suitable for non-von-Neumann architectures, processor-in-memory, etc. The switching time of the gate is ~200 ps and the energy dissipation per gate operation is ~225 aJ. Cascading of successive stages is accomplished via a CMOS device which plays no role in the gate dynamics but is needed for gain to provide logic level restoration, fan-out, and isolation between input and output. This one MTJ–one CMOS design has an energy dissipation that is an order of magnitude smaller than what has been reported for traditional all-transistor xor designs.