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∘) with respect to the anisotropy axis. The drive current can be modest (106A/cm2 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.
@article{arxiv.1610.01819,
title = {Spin-torque switching and control using chirped oscillating currents},
author = {Guillaume Klughertz and Lazar Friedland and Paul-Antoine Hervieux and Giovanni Manfredi},
journal= {arXiv preprint arXiv:1610.01819},
year = {2017}
}