Skyrmions in synthetic antiferromagnet nanorings for electrical signal generation

TL;DR

This paper demonstrates that current-driven skyrmions in synthetic antiferromagnetic nanorings can achieve stable GHz frequency oscillations, making them promising for high-frequency clock devices and signal generation.

Contribution

The study introduces a novel application of SAF nanorings for stable GHz frequency skyrmion oscillations and a new skyrmionic three-phase AC alternator design.

Findings

Skyrmions in SAF nanorings exhibit stable circular motion at GHz frequencies.

Operational frequency surpasses that of ferromagnetic-heavy metal nanorings.

Performance comparable to radial Neel domain walls at low current densities.

Abstract

Current-driven magnetic skyrmions show promise as carriers of information bits in racetrack magnetic memory applications. Specifically, the utilization of skyrmions in synthetic antiferromagnetic (SAF) systems is highly attractive due to the potential to suppress the Skyrmion Hall effect, which causes a transverse displacement of driven skyrmions relative to the drift direction. In this study, we demonstrate, through analytical calculations and micromagnetic simulations, that in the case of a nanoring geometry, current-driven skyrmions achieve a stable circular motion with a constant frequency, which is a prerequisite for a skyrmion-based clock device. Notably, the operational frequency in a SAF nanoring surpasses that in a bilayer ferromagnetic-heavy metal nanoring and lies in the GHz regime for current densities of 20 MA/cm^2. We also find that the performance of skyrmions in SAF nanorings is comparable to that of radial Neel domain walls for low current densities (approximately 15 MA/cm^2) and low skyrmion densities (Nsk~6). Additionally, we introduce a novel skyrmionic three-phase AC alternator based on a SAF nanoring, which operates at frequencies in the GHz regime. Our findings underscore the potential of SAF nanorings as constituent materials in clock devices with tunable frequencies operating in the GHz regime