Topological Phase Transformation and Collapse Dynamics of Spin Textures in a Non-Centrosymmetric D_2d System

Recently a large variety of non-collinear spin textures have been revealed in various crystals with different symmetry groups. Of particular interest are crystals with D2d symmetry that exhibit a complex variety of stable and metastable spin textures that includes antiskyrmions, elliptical Bloch-skyrmions, fractional-antiskyrmions, fractional Bloch-skyrmions, and type-II trivial-bubbles. The observation of these structures necessitates their stabilization via magnetic field and temperature protocols which demands a thorough understanding of their creation, transformation, and collapse dynamics. Utilizing the real-space imaging capabilities of Lorentz transmission electron microscopy, the generation and annihilation of diverse spin textures in a single D2d Heusler compound are demonstrated. It is showed that antiskyrmions and elliptical Bloch-skyrmions can be deformed into more elaborate elongated magnetic nano-objects through a collapse mechanism. Their elongation is governed by the intrinsic antisymmetric Dzyaloshinskii-Moriya vector exchange interaction and dipolar energy present in the system. Furthermore, antiskyrmions are found to be metastable at all temperatures on field-cooling, while a topological phase transformation from elliptical Bloch-skyrmions to antiskyrmions rather takes places on field-heating. These results are corroborated by micromagnetic simulations and demonstrate the efficient manipulation of different spin textures in a D2d compound by varying field and temperature protocols and represents a critical step toward the application of magnetic skyrmions.