Phatak C, Gürsoy D
Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
Ultramicroscopy. 2015 Mar;150:54-64. doi: 10.1016/j.ultramic.2014.11.033. Epub 2014 Dec 3.
Intense ongoing research on complex nanomagnetic structures requires a fundamental understanding of the 3D magnetization and the stray fields around the nano-objects. 3D visualization of such fields offers the best way to achieve this. Lorentz transmission electron microscopy provides a suitable combination of high resolution and ability to quantitatively visualize the magnetization vectors using phase retrieval methods. In this paper, we present a formalism to represent the magnetic phase shift of electrons as a Radon transform of the magnetic induction of the sample. Using this formalism, we then present the application of common tomographic methods particularly the iterative methods, to reconstruct the 3D components of the vector field. We present an analysis of the effect of missing wedge and the limited angular sampling as well as reconstruction of complex 3D magnetization in a nanowire using simulations.
对复杂纳米磁性结构正在进行的深入研究需要对纳米物体周围的三维磁化和杂散场有基本的了解。对此类场进行三维可视化是实现这一目标的最佳途径。洛伦兹透射电子显微镜提供了高分辨率与使用相位恢复方法定量可视化磁化矢量能力的合适组合。在本文中，我们提出一种形式主义，将电子的磁相移表示为样品磁感应强度的拉东变换。利用这种形式主义，我们接着展示了常见断层扫描方法特别是迭代方法在重建矢量场三维分量方面的应用。我们通过模拟分析了缺失楔形和有限角度采样的影响以及纳米线中复杂三维磁化的重建。
