Tuning the dynamics of magnetic droplet solitons using dipolar interactions

TL;DR

This paper investigates how dipolar interactions influence magnetic droplet solitons in spin torque nano-oscillators, revealing that free layer thickness significantly affects droplet dynamics, stability, and potential for spintronic applications.

Contribution

The study extends droplet theory by systematically analyzing the effects of dipolar interactions through free layer thickness variation, providing new insights into droplet stability and nucleation boundaries.

Findings

Increasing free layer thickness raises threshold current.

Thicker layers decrease droplet frequency and size.

Thinner layers are more suitable for high-speed spintronic devices.

Abstract

Magnetic droplets are dissipative magnetodynamical solitons that can form under current driven nanocontacts in magnetic layers with large perpendicular magnetic anisotropy. Here, we extend the original droplet theory by studying the impact of the dipolar interactions on the dynamics of droplet solitons. By varying the thickness of the free layer of a spin torque nano-oscillator, we systematically tune the internal field of the free layer to investigate the dynamics of droplet solitons. Our numerical results show that increasing the free layer thickness increases the droplet threshold current, decreases the droplet frequency and diameter, enlarges the current hysteresis and also modifies the structure of the droplet. The Oersted field of the current breaks the phase coherency and deteriorates the stability of the droplet in free layers with larger thicknesses. Moreover, our findings show a simple relation to determine the impact of the free layer thickness on the droplet nucleation boundaries. Our study presents the missing brick on the physics behind magnetic droplet solitons, and further illustrates that magnetic droplets in thinner layers possess more promising characteristics for spintronic applications and enable devices with higher speed of operation.