Magnetic Force Microscopy Study Of Magnetic Nano-Materials And Exploration Of Spin Injection Into Organic Semiconductors

Magnetic materials have been employed in a truly wide range of applications such as electrical engineering, computer science, communication technology, and spintronics arisen in recent years. The development of applications requires materials with higher performance, which in turn accelerates the development of magnetism and magnetic material research. As is well known, the performance of magnetic materials is tightly related to their crystalline and magnetic microstructures. Therefore, it is of great significance to investigate their crystalline and magnetic microstructures and their correlation with material performance. Furthermore, magnetic domain research is also helpful to understand their magnetization reversal behavior and coercivity mechanism, sequentially ameliorate their manufacture technics and improve their performance. Among all magnetic sensitive imaging techniques, magnetic force microscope (MFM) is a very powerful instrument to investigate the crystalline and magnetic microstructures of magnetic materials due to its high lateral resolution (10-50 nm), low sample preparation quality requirement, simple operation, and wide range of materials applicable. Furthermore, it can capture the crystalline microstructure images and corresponding magnetic microstructure images simultaneously. These advantages make MFM the most widely used magnetic domain observation technique soon after its invention.In this thesis, crystalline and magnetic microstructures of three series of magnetic materials named Pr_yFe_90-yB₁₀ (y=8.0～11.76), Pr₆₀Al₁₀Ni₁₀Cu_20-xFe_x (0≤x≤20) and La_0.7Sr_0.3Fe_11.8Co_0.2O₁₉ (at.%) are investigated using MFM. The correlation between their crystalline and magnetic microstructures and their magnetic performance is detailedly discussed and their coercivity mechanisms are also analyzed. To further understand the imaging principle of MFM and provide theoretical reference for MFM image analysis of magnetic nanoparticles, computer simulation of MFM images and domain structure of sub-micron magnets is also performed. Besides, explore for new magnetic sensitive imaging technology with ultra-high resolution has also been tried. At last, the injection, transport and detection of spin dependent carriers in organic...