Spin-torque switching and control using chirped oscillating currents

TL;DR

This paper introduces a method using chirped oscillating spin currents to precisely control magnetization in nanomagnets, achieving stable precession and reversal with low current densities and robustness against thermal noise.

Contribution

It presents a novel approach employing chirped spin currents and a quantum-like formalism to control magnetization dynamics in nanomagnets, enabling stable precession and reversal at low currents.

Findings

Chirped spin currents induce stable magnetization precession at various angles.

Magnetization reversal is achievable with modest current densities and small external fields.

The method is robust against thermal noise at room temperature.

Abstract

We propose to use oscillating spin currents with slowly varying frequency (chirp) to manipulate and control the magnetization dynamics in a nanomagnet. By recasting the Landau-Lifshitz-Slonczewski equation in a quantum-like two-level formalism, we show that a chirped spin current polarized in the direction normal to the anisotropy axis can induce a stable precession of the magnetic moment at any angle (up to $90^\circ$) with respect to the anisotropy axis. The drive current can be modest ($10^6\,\rm A/cm^2$ or lower) provided the chirp rate is sufficiently slow. The induced precession is stable against thermal noise, even for small nano-objects at room temperature. Complete reversal of the magnetization can be achieved by adding a small external magnetic field antiparallel to the easy axis. Alternatively, a combination of chirped ac and dc currents with different polarization directions can also be used to trigger the reversal.