Room-temperature antiskyrmions and sawtooth surface textures in a noncentrosymmetric magnet with $S_4$ symmetry

TL;DR

This paper reports the discovery of room-temperature antiskyrmions in a noncentrosymmetric S4 symmetry magnet, revealing their transformation to skyrmions and surface sawtooth textures, expanding the understanding of topological spin textures.

Contribution

It introduces a new material with S4 symmetry hosting room-temperature antiskyrmions, demonstrating their stability and surface textures, which was not previously observed in this symmetry class.

Findings

Antiskyrmions exist at room temperature in the new material.

Magnetic textures' periodicity depends on crystal thickness.

Surface sawtooth fractals are observed due to dipolar and DMI interactions.

Abstract

Topological spin textures have attracted much attention both for fundamental physics and spintronics applications. Among them, antiskyrmions possess a unique spin configuration with Bloch-type and N\'eel-type domain walls due to anisotropic Dzyaloshinskii-Moriya interaction (DMI) in the noncentrosymmetric crystal structure. However, antiskyrmions have thus far only been observed in a few Heusler compounds with $D_{2\mathrm{d}}$ symmetry. Here, we report a new material Fe$_{1.9}$Ni$_{0.9}$Pd$_{0.2}$P in a different symmetry class ($S_4$ symmetry), where antiskyrmions exist over a wide temperature region including room temperature, and transform to skyrmions upon changing magnetic field and lamella thickness. The periodicity of magnetic textures greatly depends on crystal thickness, and domains with anisotropic sawtooth fractals are observed at the surface of thick crystals, which are attributed to the interplay between dipolar interaction and DMI as governed by crystal symmetry. Our findings provide a new arena to study antiskyrmions, and should stimulate further research on topological spin textures and their applications.