Current-induced Pinwheel Oscillations in Perpendicular Magnetic Anisotropy Spin Valve Nanopillars

TL;DR

This paper reports on current-induced oscillations in perpendicular magnetic anisotropy spin valve nanopillars, where large DC currents cause continuous switching of magnetic layers, resulting in MHz oscillations confirmed by simulations.

Contribution

It demonstrates a novel current-induced oscillation phenomenon in perpendicular spin valves, supported by experimental observations and micromagnetic simulations.

Findings

Oscillations occur only for one current sign.

Oscillation frequency is in the MHz range.

Behavior aligns with micromagnetic simulations.

Abstract

Nanopillar spin valve devices are typically comprised of two ferromagnetic layers: a reference layer and a free layer whose magnetic orientation can be changed by both an external magnetic field and through the introduction of spin-polarized electric current. Here we report the continuous repeated switching behavior of both the reference and free layers of a perpendicular spin valve made of Co/Pd and Co/Ni multilayers that arises for sufficiently large DC currents. This periodic switching of the two layers produces an oscillating signal in the MHz regime but is only observed for one sign of the applied current. The observed behavior agrees well with micromagnetic simulations.