Magnetization reversal processes of isotropic permanent magnets with various inter-grain exchange interactions

• Published in: AIP advances Vol. 7; no. 5; pp. 056224 - 056224-4
• Main Authors: Tsukahara, Hiroshi, Iwano, Kaoru, Mitsumata, Chiharu, Ishikawa, Tadashi, Ono, Kanta
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.05.2017; AIP Publishing LLC
• Subjects: Boundary conditions; Coercivity; Dipole interactions; Exchanging; Grain; Magnetic fields; Magnetic properties; Magnetism; Magnetization reversal; Permanent magnets
• ISSN: 2158-3226; 2158-3226
• DOI: 10.1063/1.4976950

We performed a large-scale micromagnetics simulation on a supercomputing system to investigate the properties of isotropic nanocrystalline permanent magnets consisting of cubic grains. In the simulation, we solved the Landau–Lifshitz–Gilbert equation under a periodic boundary condition for accurate calculation of the magnetization dynamics inside the nanocrystalline isotropic magnet. We reduced the inter-grain exchange interaction perpendicular and parallel to the external field independently. Propagation of the magnetization reversal process is inhibited by reducing the inter-grain exchange interaction perpendicular to the external field, and the coercivity is enhanced by this restraint. In contrast, when we reduce the inter-grain exchange interaction parallel to the external field, the coercivity decreases because the magnetization reversal process propagates owing to dipole interaction. These behaviors show that the coercivity of an isotropic permanent magnet depends on the direction of the inter-grain exchange interaction.