The need for lighter motors in increasing automobile fuel efficiency is high and NdFeB anisotropic bonded magnets with high magnetic performance and freedom of design are effective in realizing motor size and weight reductions. The magnetic powder used in NdFeB anisotropic bonded magnets is manufactured by the d-HDDR process utilizing the high temperature reaction between NdFeB and hydrogen. This bonded magnet has five times higher magnetic force than standard ferrite one and its near-net-shape characteristic enable easy application to motors. The anisotropic bonded magnet has been used for downsized / lightweight seat motors. The coercive force was improved by grain boundary diffusion treatment of Nd-Cu-Al alloy into NdFeB magnetic powders after d-HDDR treatment instead of Dy addition. This alloy forms Nd-rich grain boundaries and isolates the crystal grains after diffusion process. As a result, it intercepts the magnetic interaction between the crystal grains and leads to increase of the coercive force up to 20kOe. Currently, this anisotropic magnetic powder was molded to bonded magnet with high performance by compression molding and injection molding magnet with mixture of several resins.
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