A nanomagnets majority logic gate based on heterogeneous multiferroic structure global strain clock

Abstract

In the post-Moore era, nanomagnetic logic circuits have shown great potential to replace complementary metal oxide semiconductor (CMOS) circuits. A majority logic gate, as the core of a nanomagnetic logic circuit, is equivalent to the inverter in the CMOS circuit. A nanomagnetic logic majority gate generally has four nanomagnets arranged in a “T” shape. The nanomagnets on the three corners of the “T” (<i>I</i><sub>1</sub>, <i>I</i><sub>2</sub>, <i>I</i><sub>3</sub>) are the three inputs, and the middle nanomagnet is the output (<i>O</i>).<br>This paper proposed a nanomagnet majority logic gate based on the global strain clock of heterogeneous multiferroic, utilizing the response difference of positive and negative magnetostrictive coefficient materials (Ni, Terfenol-D) to the same strain. From bottom to top, the device is mainly composed of a silicon substrate, a piezoelectric layer, and four elliptical cylindrical nanomagnets. The piezoelectric layer's material is PMN-PT, and three input nanomagnets(I1, I2, and I3) are made of Ni, while the output nanomagnet <i>O</i> is made of Terfenol-D.<br>Besides, a two-step calculation mode of “high-stress start - low-stress calculation” was designed, that is, the <i>O</i> was first switched to the “Null” with a stress of -30Mpa, and then the stress was reduced to -15Mpa, so that the <i>O</i> could realize majority calculation under the coupling of <i>I</i><sub>1</sub>, <i>I</i><sub>2</sub>, and <i>I</i><sub>3</sub>. The micromagnetic simulation software Mumax3 was adopted to simulate the performance of the device. The results revealed that the device could successfully perform continuous majority calculation on any three-terminal input combination. By using the two-step calculation mode, the calculation accuracy of the device could reach 100%, its cycle of continuous calculation was 2.75 ns, and the cycle energy consumption was about 64aJ. It was found that the change in energy potential well caused by the change of stress anisotropy energy and dipole coupling energy was the main reason to determine the magnetization dynamic behavior of the device. Therefore, the results of this paper can provide important guidance for the design of nanomagnetic logic circuits.