Breaking the current density threshold in spin-orbit-torque magnetic random access memory

TL;DR

This paper introduces a novel current flow strategy in SOT-MRAM that significantly lowers the reversal current density threshold, enabling faster, field-free, and more energy-efficient magnetic switching.

Contribution

It presents a new reversal method using a constant magnitude but varying flow direction of current, reducing the threshold by over the Gilbert damping coefficient and deriving optimal reversal paths.

Findings

Reversal current density threshold reduced by over the Gilbert damping coefficient.

Theoretical minimal reversal current density is around 10^5 A/cm^2.

No external magnetic field needed for deterministic reversal.

Abstract

Spin-orbit-torque magnetic random access memory (SOT-MRAM) is a promising technology for the next generation of data storage devices. The main bottleneck of this technology is the high reversal current density threshold. This outstanding problem of SOT-MRAM is now solved by using a current density of constant magnitude and varying flow direction that reduces the reversal current density threshold by a factor of more than the Gilbert damping coefficient. The Euler-Lagrange equation for the fastest magnetization reversal path and the optimal current pulse are derived for an arbitrary magnetic cell. The theoretical limit of minimal reversal current density and current density for a GHz switching rate of the new reversal strategy for CoFeB/Ta SOT-MRAMs are respectively of the order of $10^5$ A/cm$^2$ and $10^6$ A/cm$^2$ far below $10^7$ A/cm$^2$ and $10^8$ A/cm$^2$ in the conventional strategy. Furthermore, no external magnetic field is needed for a deterministic reversal in the new strategy.