Modeling of stress-regulated AND (OR) logic gate based on flipping preference of tilted nanomagnet
Authors: Liu Jia-Hao  , Yang Xiao-Kuo  , Wei Bo  , Li Cheng  , Zhang Ming-Liang  , Li Chuang  , Dong Dan-Na  ,   1. Department of Basic Sciences, Air Force Engineering University, Xi'an 710051, China;,   2. Wired Communications Department, Air Force Communications NCO Academy, Dalian 116100, China
Published: December 2020

Nano-magnetic logic device (NMLD) is a novel nanoelectronic device that stores, processes, and transfers information by dipole-coupled magneto-static interactions between nanomagnets. In the NMLD, long axis tilted nanomagnet attracts the attention of researchers due to its flexibility in magnetic logic design. Edge-slanted nanomagnet is wildly used, whose long axis is tilted due to its asymmetric shape. However, there are three defects in edge-slanted nanomagnets. 1) This type of nanomagnet requires a larger size, thus increasing the nano-magnetic logic (NML) space and introducing the C-shape and vortex clock errors that are often found in large-sized nanomagnets. 2) The irregular shape of nanomagnet increases the requirements for fabrication. 3) Complex calculations caused by the irregular shape are inevitable.</br>In this paper, the tilt of the long axis of the nanomagnet is realized by placing the regular-shaped (elliptical cylinder) nanomagnet (50 nm×100 nm×20 nm) obliquely. According to the flipping preference of tilted nanomagnet, the authors design a two-input AND (OR) logic gate clocked by stress. The authors choose PMN-PT (Pb (Mg<sub>1/3</sub>Nb<sub>2/3</sub>) O<sub>3</sub>-PbTiO<sub>3</sub>) as the piezoelectric layer material to use its high piezoelectric coefficient. For magnetic materials, the authors choose Terfenol-D (Tb<sub>0.7</sub>Dy<sub>0.3</sub>Fe<sub>2</sub>), whose magnetic crystal anisotropy is smaller. The material of the subatrate is not discussed in this paper, which will be further studied in future experimental work. The mathematical model is established, and the dynamic magnetization of the gate is calculated. A stress of 90 MPa is applied to the output nanomagent for 3 ns. The nanomagnet is flipped to “NULL” at 1.8 ns and is then flipped to the final stable state after the stress has been removed for 0.9 ns. The output will become logic “0” (“1”) only if the input is logic “00” (“11”), otherwise the output will be logic “1” (“0”), thus successfully implementing OR (AND) logic. In addition, the gate is simulated by using the micromagnetic method. The results are basically consistent with our model. Unlike the designs based on edge-slanted nanomagnets, the basic logic gate based on tilted nanomagnets has three advantages. 1) This design allows high-aspect-ratio (2:1) nanomagnets to be used in logic functions. Therefore, less vortex and C-shaped error will be generated. 2) The regular shape can reduce the fabrication requirements and computational complexities. 3) Using stress as a clock, the energy consumption is greatly reduced, which can be only one-tenth of the general designs clocked by spin electronics.</br>This model provides a greater energy efficiency and reliable basic logic unit for NML design. In the experimental preparation, there may be a large preparation error tilting the nanomagnet. As a solution, the stress electrodes can be tilted instead. So the stress will also make an angle with respect to the long axis of the nanomagnet.