Search

This paper presents a ternary content-addressable memory (TCAM) cell based on a skewed straintronic magnetotunneling junction (MTJ) switch. A straintronic magnetotunneling junction (s-MTJ) is a three-terminal switch, where the resistance between two of the terminals switches when a potential is applied to the third (gate) terminal that induces strain in the magnetostrictive free-layer. An s-MTJ is a highly energy-efficient switch that would dissipate only ~aJ of energy during switching. This paper discusses a novel variant of s-MTJ, namely skewed s-MTJ (ss-MTJ), where the MTJ switching can be controlled by two gate terminals. The current through an ss-MTJ is minimum when the potentials at the first and second gate terminals ( V2 and V3 , respectively) obey the relation V3 = V2+VF . Here, VF is a fixed voltage (“offset voltage”). Current in an ss-MTJ increases steeply when V2 and V3 deviate from the above “match” condition. This unconventional I – V characteristic of an ss-MTJ is exploited to design a non-Boolean TCAM cell based on just one transistor, one trench capacitor, and one ss-MTJ. We also discuss search and write operations in the ss-MTJ-TCAM cell, and show that the cell requires very small voltages to operate because of the unique I – V characteristics of the ss-MTJ. [ABSTRACT FROM PUBLISHER]

Modulation of stress anisotropy of magnetostrictive nanomagnets with strain offers an extremely energy-efficient method of magnetization reversal. The reversal process, however, is often incoherent and hence, error-prone in the presence of thermal noise at room temperature. Occurrence of incoherent metastable states in the potential landscape of the nanomagnet can further exacerbate the error. Stochastic micromagnetic simulations at room temperature are used to understand and calculate energy dissipations and switching error probabilities in this important magnetization switching methodology. We find that these quantities have an intriguing dependence on nanomagnet size. Small nanomagnets perform better owing to the fact that they are more resilient to the formation of metastable states and magnetization dynamics in them is more coherent. However, for a fixed stress anisotropy energy density, smaller nanomagnets will also have poorer resilience against thermal instability. Thus, the challenge in straintronics is to maximize the stress anisotropy energy density by developing materials and processes that yield the largest magnetostriction. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]