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 Néel-type domain walls owing to anisotropic Dzyaloshinskii–Moriya interaction in the non-centrosymmetric crystal structure. However, antiskyrmions have thus far only been observed in a few Heusler compounds with D_2d symmetry. Here we report a new material, Fe_1.9Ni_0.9Pd_0.2P, in a different symmetry class (S₄), in which antiskyrmions exist over a wide temperature range that includes room temperature, and transform into skyrmions on changing magnetic field and lamella thickness. The periodicity of magnetic textures greatly depends on the crystal thickness, and domains with anisotropic sawtooth fractals were observed at the surface of thick crystals and attributed to the interplay between the dipolar interaction and the Dzyaloshinskii–Moriya interaction as governed by crystal symmetry. Our findings provide an arena in which to study antiskyrmions, and should stimulate further research on topological spin textures and their applications.

拓扑自旋纹理在基础物理学和自旋电子学应用中引起了广泛关注。其中，由于非中心对称晶体结构中的各向异性 Dzyaloshinskii-Moriya 相互作用，antiskyrmions 具有独特的自旋构型，具有 Bloch 型和 Néel 型畴壁。然而，到目前为止，antiskyrmions 仅在少数具有D _{2 d}对称性的 Heusler 化合物中观察到。在这里，我们报告了一种新材料，Fe _1.9 Ni _0.9 Pd _0.2 P，具有不同的对称性类别 ( S ₄)，其中反斯格明子存在于包括室温在内的广泛温度范围内，并在磁场和薄片厚度变化时转变为斯格明子。磁性结构的周期性在很大程度上取决于晶体厚度，在厚晶体的表面观察到具有各向异性锯齿形分形的畴，这归因于偶极相互作用与受晶体对称性控制的 Dzyaloshinskii-Moriya 相互作用之间的相互作用。我们的发现提供了一个研究 antiskyrmions 的舞台，应该会刺激对拓扑自旋纹理及其应用的进一步研究。