Understanding the magnetic phase diagram in capped MnSi thin films

Skyrmions are a topologically non-trivial magnetisation pattern that form in crystal structures whose broken inversion symmetry gives rise to the Dzyaloshinsky-Moriya interaction (DMI). Their robustness against thermal fluctuations make them ¿ in thin film form - attractive candidates for non-volatile memory devices. While bulk crystals of skyrmion materials have been well studied, the picture in thin films is still rather controversial due to added complications such as epitaxial strain, surface anisotropy, and magnetic biasing effects. We propose to use polarised neutron reflectometry to resolve the key features of the thin-film skyrmion phase diagram, investigating the twisting of magnetisation vectors that arises. In particular we hope to be able to unravel the influence of the interfaces on the magnetic state of the film in terms of their structural and magnetic effects.斯格明子（Skyrmions）是一类拓扑非平庸的磁化构型，可在破缺反演对称性的晶体结构中形成，此类体系会产生德热沃夏斯基-莫里亚相互作用（Dzyaloshinsky-Moriya interaction，DMI）。其抗热涨落的优异稳定性，使得以薄膜形式存在的斯格明子成为非易失性存储器件的极具潜力的候选材料。尽管斯格明子材料的块体晶体已得到充分研究，但由于外延应变、表面各向异性以及磁偏置效应等额外复杂因素的影响，薄膜体系中的相关物理图像仍存在较大争议。本研究拟采用极化中子反射术（polarised neutron reflectometry）解析薄膜斯格明子相图的关键特征，探究体系中磁化矢量的扭转行为；尤其希望能够从结构与磁学效应的维度，厘清界面对薄膜磁学状态的调控作用。