Observation of hedgehog skyrmions in sub-100 nm soft magnetic nanodots

TL;DR

This study reports the first observation of stable hedgehog skyrmions in soft magnetic permalloy nanodots at room temperature, without Dzyaloshinskii-Moriya interaction, expanding potential for skyrmion-based spintronic devices.

Contribution

It demonstrates the existence and stabilization of non-chiral hedgehog skyrmions in soft magnetic nanodots without DMI or perpendicular anisotropy, confirmed by experiments and simulations.

Findings

Hedgehog skyrmions observed at room temperature in permalloy nanodots.

Skyrmions stabilized by magnetic fields from MFM probes.

Existence of metastable Neel skyrmions confirmed through simulations.

Abstract

Magnetic skyrmions are nanometric spin textures of outstanding potential for spintronic applications due to unique features governed by their non-trivial topology. It is well known that skyrmions of definite chirality are stabilized by the Dzyaloshinskii-Moriya exchange interaction (DMI) in bulk non-centrosimmetric materials or ultrathin films with strong spin-orbit coupling in the interface. In this work, we report on the detection of magnetic hedgehog-skyrmions at room temperature in confined systems with neither DMI nor perpendicular magnetic anisotropy. We show that soft magnetic (permalloy) nanodots are able to host non- chiral hedgehog skyrmions that can be further stabilized by the magnetic field arising from the Magnetic Force Microscopy probe. Analytical calculations and micromagnetic simulations confirmed the existence of metastable N\'eel skyrmions in permalloy nanodots even without external stimuli in a certain size range. Our work implies the existence of a new degree of freedom to create and manipulate skyrmions in soft nanodots. The stabilization of skyrmions in soft magnetic materials opens a possibility to study the skymion magnetization dynamics otherwise limited due to the large damping constant coming from the high spin-orbit coupling in materials with high magnetic anisotropy.