Current-driven vortex oscillations in metallic nanocontacts: Zero-field oscillations and training effects

TL;DR

This paper investigates current-driven vortex oscillations in nanocontacts, demonstrating their persistence at zero magnetic field and exploring training effects on their frequency and linewidth.

Contribution

It provides both experimental and theoretical insights into zero-field vortex oscillations and their behavior under small in-plane magnetic fields.

Findings

Vortex oscillations occur at 250-500 MHz due to giant-magnetoresistance variations.

Oscillations persist at zero magnetic field after nucleation at large perpendicular fields.

Training effects influence oscillation frequency and linewidth.

Abstract

We present an experimental and theoretical study of the low-field dynamics of current-driven vortex oscillations in nanocontacts based on spin-valve multilayers. These oscillations appear as low-frequency (250-500 MHz) excitations in the electrical power spectrum which arise from to variations in the giant-magnetoresistance. We show that the vortex oscillations, once nucleated at large fields applied perpendicular to the film plane, persist at zero applied magnetic fields. Some training effects on the oscillation frequency and linewidth also observed for small in-plane magnetic fields.