Spin Transfer Dynamics in Spin Valves with Out-of-plane Magnetized CoNi Free Layers

TL;DR

This study investigates spin transfer-induced dynamics in nanocontact devices with out-of-plane magnetized CoNi free layers, confirming theoretical models and estimating key parameters like spin torque asymmetry and spin wave losses.

Contribution

It provides experimental validation of the single-domain model for out-of-plane magnetized free layers and estimates the spin torque asymmetry parameter and spin wave radiation loss.

Findings

Frequencies and powers match single-domain model predictions.

Precessional orbits range from zero to 90 degrees with increasing current.

Estimated spin torque asymmetry parameter lambda ~ 1.5.

Abstract

We have measured spin transfer-induced dynamics in magnetic nanocontact devices having a perpendicularly magnetized Co/Ni free layer and an in-plane magnetized CoFe fixed layer. The frequencies and powers of the excitations agree well with the predictions of the single-domain model and indicate that the excited dynamics correspond to precessional orbits with angles ranging from zero to 90 degrees as the applied current is increased at a fixed field. From measurements of the onset current as a function of applied field strength we estimate the magnitude of the spin torque asymmetry parameter lambda ~ 1.5. By combining these with spin torque ferromagnetic resonance measurements, we also estimate the spin wave radiation loss in these devices.