Spin–Orbit Torque and Dipole Coupling for Nanomagnetic Array Programmability

Nance, J. A., Roxy, K. A., Bhanja, S., & Carman, G. P. (2020). Spin-Orbit Torque and Dipole Coupling for Nanomagnetic Array Programmability. IEEE Transactions on Magnetics.

Abstract: Computational architectures that rely on an array of dipole-coupled nanomagnetic elements require an energy-efficient method of programming individual elements within the array. As a low-energy, selective method of controlling magnetization, spin–orbit torque (SOT) represents a promising solution. Here, a finite-difference micromagnetic model is used to characterize the dipole coupling between adjacent CoFeB nanodisks and to determine the critical SOT current required to switch these disks. Additionally, a phase plot showing disk dimensions at which both vortex and single-domain in-plane magnetic states are stable is produced. A dipole-coupled array’s response to dynamic application of SOT current is also simulated. The results show that the rate of applying SOT current to one element in the array strongly influences the stable states of adjacent elements and that the SOT current amplitude required for this influence is an order of magnitude lower than the previously determined critical switching current. This indicates that SOT current dynamics play a significant role in the behavior of a dipole-coupled array. Finally, an architecture to achieve programmability in nanomagnetic computational platforms with SOT is presented.