# Skyrmion Based Spin-Torque Nano-Oscillator

## TL;DR

This paper uses micromagnetic simulations to explore how skyrmion dynamics in a nanodot can be controlled via material parameters and geometry, leading to improved spin-torque nano-oscillator performance.

## Contribution

It demonstrates that adjusting uniaxial anisotropy and nanodot radius can enhance skyrmion velocity and oscillator frequency while preventing annihilation, providing new design insights.

## Key findings

- Lowering $K_u$ increases skyrmion velocity.
- Modifying edge $K_u$ prevents skyrmion annihilation at high currents.
- Gyration frequency correlates with skyrmion velocity, validated by linear fitting.

## Abstract

Using micromagnetic simulation, we investigate the self-sustained oscillation of magnetic skyrmion in a ferromagnetic circular nanodot, driven by spin-torque which is generated from a reference layer of a circular nanopillar device. We demonstrate, by lowering the value of uniaxial anisotropy constant ($K_u$), the velocity of the skyrmion can be increased and using this property, gyration frequency of the skyrmion oscillator can be enhanced. Annihilation of the skyrmion at higher current densities, limit the gyration frequency of the oscillator, whereas by modifying the $K_u$ value at the edge of nanodot, we are able to protect the skyrmion from being annihilated at higher current densities which in turn, increases the gyration frequency of the skyrmion based oscillator. By linear fitting the velocity value, obtained from the motion of the skyrmion in a nanostrip, we also predict the gyration frequency of the skyrmion in the nanodot which proves the validity of our idea in an intuitive way. We have also varied the radius of the nanodisk to see its effect on skyrmion.