Atomic resolution determination of spin configuration at interfaces in functional materials in the transmission electron microscope

新的节能信息和通信技术对磁性材料的性能提出了越来越高的要求。为了应对这些挑战，材料的开发需要对它们的局部自旋构型有原子级的了解，以便预测和控制它们的物理性质。在这个中德联合研究项目中，我们将发展功能材料界面自旋组态的原子尺度磁成像和光谱学，以获得对新型磁耦合现象的物理起源的基本理解。我们的方法涉及使用离轴电子全息（EH），电子磁圆二色性（EMCD），空间分辨电子能量损失光谱和色差校正的组合。色差校正，特别是，有可能提高空间分辨率的磁特性使用EH和EMCD的原子水平。这些技术的结合使用有望提供原子尺度的信息，在同一材料的面内和面外的磁化，从而提供三维自旋信息的高空间分辨率。自旋，电荷，轨道和晶格自由度之间的合作相互作用的界面将导致在原子水平上的实验理解交换弹簧磁铁，铁磁和铁电材料之间的界面处的磁电耦合，反铁磁和铁磁材料之间的界面处的交换偏置和磁性薄膜和衬底之间的界面处的磁死层。由于像差校正透射电子显微镜固有地提供局部结构和组成信息的访问，所测量的自旋配置将与局部原子排列、应变分布、元素扩散、化学键合、电荷转移、轨道耦合和原子水平上的对称性破缺相关。这种方法的结合将有助于详细的基本理解的物理起源的磁性材料的性质在原子尺度上，并将导致新的设计的磁性材料的未来应用与改进的设备功能。

New energy-efficient information and communications technologies place ever-increasing demands on the performance of magnetic materials. The development of materials to meet these challenges requires an atomic-level knowledge of their local spin configurations, in order to predict and control their physical properties. In this Joint Sino-German Research Project, we will develop atomic-scale magnetic imaging and spectroscopy of the spin configurations at interfaces in functional materials, in order to obtain a fundamental understanding about the physical origins of novel magnetic coupling phenomena. Our approach involves the use of a combination of off-axis electron holography (EH), electron magnetic circular dichroism (EMCD), spatially-resolved electron energy-loss spectroscopy and chromatic aberration correction. Chromatic aberration correction, in particular, has the potential to improve spatial resolution in magnetic characterisation using both EH and EMCD to the atomic level. The combined use of these techniques promises to provide atomic-scale information about both in-plane and out-of-plane magnetization in the same material, thereby offering three-dimensional spin information at the high spatial resolution. The cooperative interplay between spin, charge, orbital and lattice degrees of freedom at interfaces will results in an atomic level experimental understanding of exchange spring magnets, magnetoelectric coupling at interfaces between ferromagnetic and ferroelectric materials, exchange bias at interfaces between antiferromagnetic and ferromagnetic materials and magnetically dead layers at interfaces between magnetic thin films and substrates. Since aberration corrected transmission electron microscopy inherently provides access to local structural and compositional information, the measured spin configurations will be correlated with local atomic arrangements, strain distributions, elemental diffusion, chemical bonding, charge transfer, orbital coupling and symmetry breaking at the atomic level. This combination of methods will contribute to a detailed fundamental understanding of the physical origins of the properties of magnetic materials at the atomic scale and will lead to new designs of magnetic materials for future applications with improved device functionality.