Effect of Nanomagnet Geometry on Reliability, Energy Dissipation, and Clock Speed in Strain-Clocked DC-NML
Md Mamun Al-Rashid, Dhritiman Bhattacharya, Supriyo Bandyopadhyay, Jayasimha Atulasimha · IEEE Transactions on Electron Devices · 2015
Strain-clocked dipole-coupled nanomagnetic logic (DC-NML) is an energy-efficient Boolean logic paradigm whose progress has been stymied by its propensity for high error rates. In an effort to mitigate this problem, we have studied the effect of nanomagnet geometry on error rates, focusing on elliptical and cylindrical geometries. We had previously reported that in elliptical nanomagnets, the out-of-plane excursion of the magnetization vector during switching creates a precessional torque that plays a dual role-it speeds up the switching, but is also responsible for the high switching error probability. The absence of this torque in cylindrical magnets should lower error rates, but our simulations show that the error rate actually does not improve significantly compared with elliptical magnets while the switching becomes unacceptably slow. Here, we show that DC-NML employing elliptical nanomagnets can offer relatively high reliability for NML (switching error probability <;$10^{-8}$ ), moderate clock speed ($\sim 100$ MHz), and two to three orders of magnitude energy saving compared with CMOS devices, provided the shape anisotropy energy barrier of the nanomagnet is increased to at least $\sim 5.5$ eV to allow engineering a stronger dipole coupling between neighboring nanomagnets.