Magnetic Skyrmions for Cache Memory

Abstract: Magnetic skyrmions (MS) are particle-like spin structures with whirling configuration, which are promising candidates for spin-based memory. MS contains alluring features including remarkably high stability, ultra low driving current density, and compact size. Due to their higher stability and lower drive current requirement for movement, skyrmions have great potential in energy efficient spintronic device applications. We propose a skyrmion-based cache memory where data can be stored in a long nanotrack as multiple bits. Write operation (formation of skyrmion) can be achieved by injecting spin polarized current in a magnetic nanotrack and subsequently shifting the MS in either direction along the nanotrack using charge current through a spin-Hall metal (SHM), underneath the magnetic layer. The presence of skyrmion can alter the resistance of a magnetic tunneling junction (MTJ) at the read port. Considering the read and write latency along the long nanotrack cache memory, a strategy of multiple read and write operations is discussed. Besides, the size of a skyrmion affects the packing density, current induced motion velocity, and readability (change of resistance while sensing the existence of a skyrmion). Design optimization to mitigate the above effects is also investigated.