Analysis of Magnetization Reversal Process of Nd–Fe–B Sintered Magnets by Magnetic Domain Observation Using Kerr Microscope
We used a Kerr microscope, image processing, and photo editing to clarify magnetization reversal and its propagation in a sintered Nd-Fe-B magnet. Magnetic domain change was observed when a dc field from +20 to 20 kOe was applied to a sintered Nd-Fe-B magnet. Simultaneous magnetization reversal in several grains along the easy axis direction and its propagation to neighboring grains occurred. This indicates that the nucleation field in a grain and magnetic interaction between grains are important controlling factors of the coercivity of sintered Nd-Fe-B magnets.
Nucleation regions and coercivity determination of sintered Nd-Fe-B magnets
This paper describes the use of magnetic force microscopy MFM to observe magnetization reversal and nucleation in sintered permanent magnet materials. The investigated magnet is sintered Nd-Fe-B magnet. The domain structure is observed in both perpendicular and parallel surfaces to the alignment axis (easy axis) in a thermally demagnetized state. Maze-like and stripe-like magnetic domains are observed in perpendicular and parallel surfaces respectively. The nucleation regions are successfully observed at domain walls and presented in 3D with clear magnetic contrast images. The sample shows narrow magnetic domains with negative nucleation regions. The volume of nucleation site are determined and validated theoretically by developing an approach involving coercivity versus nucleus volume. It is shown that nucleation volume is proportional to coercive field. These insights can be useful for realizing Dy free Nd-Fe-B magnet with high coercivity.
Persius and the Programmatic Satire: A Study in Form and Imagery
Introduction 1. Style and expression in Persius' fifth satire 2. The programmatic satire and the method of Persius I 3. The nature and sources of Persius' imagery 4. Persius' first satire: analysis 5. Grandeur and humility: Juvenal and the high style Appendixes Text Translation Index of modern authors Index locorum potiorum Index of images, topics and words.