Logic gates are devices used for implementing Boolean functions. Based on binary inputs, they perform logic operations and thereby give single output. They form the basis of logic circuits such as multiplexers and other electronics devices. Logic functions include AND, OR, NOT, NAND, NOR, XOR, and XNOR. Several methods are available for implementing these logic functions.
Magnetic skyrmion generated from ferromagnetic layer surface is one of the methods used for implementing logic functions. It can be used for ultra-high-density and ultra-low-energy logic gates with data nonvolatility and topological stability. The rapid advancement in technology has resulted into increased demand for more-powerful, smaller, reliable and less expensive integrated circuits. This can be achieved by creating devices that are adapted to various logic operations and functions and are capable of performing such functions to completeness.
A group of researchers led by Professor Long You at Huazhong University of Science and Technology, School of Optical and Electronic Information in China, in collaboration with Dr. Min Song from Hubei University and Dr. Nuo Xu from University of California, Berkeley, proposed the use of skyrmion for complete implementation of various logic functions and operations. It is based on manipulating the effects of skyrmion Hall effect, spin-orbit torque (SOT), voltage control of magnetic anisotropy (VCMA), and skyrmion-edge repulsions to determine the moving trajectories of the skyrmion. Their research work is currently published in the research journal, Nano Letters.
The authors utilized interaction between skyrmions in the ferromagnetic film and single skyrmion motion for the proposed logic devices. The approach simplified the overall design and operation of the whole devices. Object-oriented micromagnetic framework based micromagnetic simulation was used for studying the dynamic behaviors of the skyrmions.
The authors successfully implement all the logic functions on the skyrmion logic gates that is, AND, OR, NOT, NAND, NOR, XOR, and NXOR. Reconfiguration of the logic functions was performed by controlling the terminal voltages integrated on a single skyrmion device, thereby generating reconfigurable skyrmion logic gates. The voltages were applied to the devices’ selected specific regions, varying the local anisotropy energy of the ferromagnetic film. Additionally, they realized that reconfigurable skyrmion logic gates are better for providing design and optimization guidelines as well as energy efficient computing for new logic families as compared to others. It is attributed to the geometrical scaling and material properties of the devices.
According to the authors, reconfigurable skyrmion logic will significantly advance the computing applications fields as it is excellent for design and creation of significantly smaller, energy efficient and non-volatile devices. These observations and conclusions were derived from the results obtained from the micromagnetic simulations.
Luo, S., Song, M., Li, X., Zhang, Y., Hong, J., Yang, X., Zou, X., Xu, N., & You, L. (2018). Reconfigurable Skyrmion Logic Gates. . Nano Letters, 18(2), 1180-1184.Go To Nano Letters