Geometry Effects in Switching of Nanomagnets with Strain: Reliability, Energy Dissipation and Clock Speed in Dipole-Coupled Nanomagnetic Logic

Abstract

Strain-clocked dipole-coupled nanomagnetic logic 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 the out-of-plane excursion of the magnetization vector during switching creates a precessional torque that is responsible for high switching error probability in elliptical nanomagnet geometries. The absence of this torque in cylindrical magnets portends lower error rates, but our simulations show that the error rate actually does not improve significantly compared to elliptical magnets while the switching becomes unacceptably slow. Here, we show that dipole coupled nanomagnetic logic can offer relatively high reliability (switching error probability < 10^-8), moderate clock speed (~ 100 MHz) and 2-3 orders of magnitude energy saving compared to CMOS devices, provided the shape anisotropy energy barrier of the magnet is increased to at least ~5.5 eV to allow engineering a stronger dipole coupling between neighboring nanomagnets.