Phase Contrast Imaging: Lorentz Transmission Electron Microscopy

This lecture provides an in-depth overview of Lorentz Transmission Electron Microscopy (LTEM) and its applications in studying magnetic domain structures and magnetization reversal mechanisms. The instructor begins by explaining the Lorentz force and its significance in LTEM imaging, followed by a discussion of various imaging modes, including Fresnel and Foucault modes. The lecture emphasizes the mathematical foundations of LTEM, including the quantum mechanical description of phase shifts and the Transport of Intensity Equations (TIE) used for quantitative analysis. The instructor illustrates how to model magnetic images and extract quantitative information about magnetic properties from LTEM observations. The second half of the lecture focuses on practical applications, showcasing examples of magnetic domain structures in ferromagnetic materials and the use of simulations to enhance understanding. The lecture concludes with a discussion on the challenges and considerations in performing TIE analysis, highlighting the importance of defocus and resolution in obtaining accurate phase measurements.