透射电镜在磁性斯格明子领域的应用

Transmission electron microscopy study on topological magnetic skyrmions

介绍了透射电镜研究磁性斯格明子的原理,以及利用透射电镜结合温度、电流、磁场等外场原位技术协同调控拓扑磁畴结构的方法。该调控方法不仅可以高分辨率表征静态磁性斯格明子的自旋组态,还可以原位、实时展示外场调控的动力学过程,具有在实空间、原位、实时、高分辨率解析斯格明子演变的优势。综述了该方法在中心对称块体、对称性破缺材料和铁磁薄膜等3个主要磁性材料体系中,对拓扑磁畴结构的调控作用。获得了宽温区、高密度、零场非易失性的斯格明子,分析了拓扑磁畴结构的温度稳定性、高密度和非易失性,揭示了磁各向异性对斯格明子自旋组态和密度影响的物理机制和规律。透射电镜所具有的纳米尺度高分辨分析磁畴结构以及原位外场调控的优势将有助于磁涡旋、磁麦纫、磁性斯格明子、磁泡等多种新型拓扑磁畴结构的分析和探索。

In this review article,the principle of Fresnel magnetic imaging and together with the manipulation methods by electric currents,magnetic fields,and temperatures in Lorentz transmission electron microscopy(L-TEM)is introduced at the beginning.The manipulation method has the advantages of in-situ characterization topological skyrmions with high-resolution in real space.The experimental results by using the manipulation method in centrosymmetric,symmetry-broken bulk magnets and ferromagnetic multilayers have been respectively reviewed.The realization of high-density,zero-field,nonvolatile topological states in broadened temperature range broke through the bottleneck of requiring the magnetic fields to stabilize skyrmions as information bits just near the phase transition temperature in previous studies.The generation mechanism of topological skyrmion has been revealed by studying the critical role of magnetic anisotropy on the spin configuration texture and the density of topological domains.The advantages of L-TEM in characterizing the magnetic domains accelerate the discovery of various topological states such as magnetic vortex,meron,skyrmion and magnetic bubble and new magnetic materials.