Vortex precession frequency and its amplitude-dependent shift in cylindrical nanomagnets

TL;DR

This paper analytically investigates the vortex precession frequency and its amplitude-dependent shift in cylindrical nanomagnets, revealing size-dependent behavior crucial for spintronic device design and magnetic nanostructure characterization.

Contribution

It introduces a collective-variable approach to analytically compute vortex precession frequency and shift across various cylinder geometries, including zero-shift conditions.

Findings

Frequency shift is positive in large dots.

Frequency shift becomes negative in smaller, elongated dots.

Zero frequency shift occurs at specific dimensions, enhancing oscillator stability.

Abstract

Frequency of free magnetic vortex precession in circular soft ferromagnetic nano-cylinders (magnetic dots) of various sizes is an important parameter, used in design of spintronic devices (such as spin-torque microwave nano-oscillators) and characterization of magnetic nanostructures. Here, using a recently developed collective-variable approach to non-linear dynamics of magnetic textures in planar nano-magnets, this frequency and its amplitude-dependent shift are computed analytically and plotted for the full range of cylinder geometries. The frequency shift is positive in large planar dots, but becomes negative in smaller and more elongated ones. At certain dot dimensions a zero frequency shift is realized, which can be important for enhancing frequency stability of magnetic nano-oscillators.