Radially-Anisotropic Rare-Earth Bonded-Magnets Prepared by Molecular Chain Alignment of Self-Organized Binder

Abstract

Magnetic properties of radially-anisotropic ring-shaped magnets were deteriorated when their outer-diameter is decreased down. Therefore, anisotropic Nd₂Fe₁₄B bonded-magnets have not been mainly applied to small motors up to now. In order to overcome the above difficulty, we developed a new technique using self-organization of binder which enabled the alignment of molecular-chain. By using this technique, we controlled the flexibility of Nd₂Fe₁₄B /Sm₂Fe₁₇N₃ rigid sheet-magnets (approximately 1 mm in thickness), transformed them into various shapes, and succeeded in preparing radially-anisotropic ring- or arc-shaped magnets. Optimizations of the solidification process of the binder under a transverse alignment-field and the transformation process into various specific shapes realized radially-anisotropic magnets with superior properties such as values of (BH)_max and also magnetic stabilities. Their value of (BH)_max exceeded 160 kJ/m³, even if their outer diameter is less than 25 mm.