Oriented 3D Magnetic Biskyrmions in MnNiGa Bulk Crystals.

Li, Xiyang; Zhang, Shilei; Li, Hang; Venero, Diego Alba; White, Jonathan S; Cubitt, Robert; Huang, Qingzhen; Chen, Jie et al. · Adv Mater · 2019

basic_science · Level V

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Abstract

A biskyrmion consists of two bound, topologically stable, skyrmion spin textures. These coffee-bean-shaped objects are observed in real space in thin plates using Lorentz transmission electron microscopy (LTEM). From LTEM imaging alone, it is not clear whether biskyrmions are surface-confined objects, or, analogous to skyrmions in noncentrosymmetric helimagnets, 3D tube-like structures in a bulk sample. Here, the biskyrmion form factor is investigated in single- and polycrystalline-MnNiGa samples using small-angle neutron scattering. It is found that biskyrmions are not long-range ordered, not even in single crystals. Surprisingly all of the disordered biskyrmions have their in-plane symmetry axis aligned along certain directions, governed by the magnetocrystalline anisotropy. This anisotropic nature of biskyrmions may be further exploited to encode information.