Powder characteristics and magnetic properties of iron-based fine particles. Effect of particle morphology and packing.:Effect of Particle Morphology and Packing

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For high-density audio/video recording-use iron-based fine acicular parti-cles, prepared from almost the same dimensional goethite industrially, the relation between the powder characteristics and the reversal properties of the magnetiza-tion was theoretically and experimentally investigated.<BR>First, it was shown that the particles studied here are of the so-called skeleton type: In the case of the particles of α-Fe, they consist of the crystal grains of order of 100 or 300Å, belonging to the BCC. phase crystallographically. Next, it was proposed to represent this type of the particle morphology and the reversal of the magnetization by a modification of Jacobs and Bean's "chain-of-spheres" fanning model. In this morphological model-scheme for the reversal of the magnetization, it was found that the dipole conformation plays a very important role and the most physically available one is strongly dependent on the particle morphology. It was also found that the local aggregate structure of the particles affects the re-versal of the magnetization: Usually, the aggregates such as so-called "multiple" or "bundle" lead to the extremely large lowering of the coercivity.<BR>Finally, the interparticle-interaction effect on the reversal of the magnetization was also investigated under a hypothesis that assumes a formation of an infinite regular space-lattice of the particles. Comparison with experiments was also tried.
日本素材物性学会の論文