Optimal protocol for spin-orbit torque switching of a perpendicular nanomagnet

TL;DR

This paper uses optimal control theory to design energy-efficient current pulses for switching a perpendicular nanomagnet via spin-orbit torque, balancing speed and energy consumption.

Contribution

It analytically derives optimal current pulse shapes that minimize energy use during magnet reversal, revealing a balanced torque component for efficient switching.

Findings

Optimal current pulses reduce Joule heating during switching.

A balanced field-like and damping-like torque enhances efficiency.

Down-chirped rotating pulses achieve robust switching without precise timing.

Abstract

It is demonstrated by means of the optimal control theory that the energy cost of the spin-orbit torque induced reversal of a nanomagnet with perpendicular anisotropy can be strongly reduced by proper shaping of both in-plane components of the current pulse. The time-dependence of the optimal switching pulse that minimizes the energy cost associated with Joule heating is derived analytically in terms of the required reversal time and material properties. The optimal reversal time providing a tradeoff between the switching speed and energy efficiency is obtained. A sweet-spot balance between the field-like and damping-like components of the spin-orbit torque is discovered; it permits for a particularly efficient switching by a down-chirped rotating current pulse whose duration does not need to be adjusted precisely.