Exchange coupling between soft magnetic ferrite and hard ferromagnetic Sm2Fe17N3 in ferrite/Sm2Fe17N3 composites

• Main Authors: N. Imaoka, E. Kakimoto, K. Takagi, K. Ozaki, M. Tada, T. Nakagawa, M. Abe
• Format: Article
• Language: English
• Published: AIP Publishing LLC 2016-05-01
• Series: AIP Advances
• Online Access: http://dx.doi.org/10.1063/1.4944519

In our previous work, we succeeded in fabricating ferrite/Sm2Fe17N3 composite magnets from explosive-consolidating Sm2Fe17N3 powders (2μm size) which were coated with a continuous iron ferrite layer (50nm thick) in an aqueous solution. The magnetization curves had no inflection, which suggests that the soft magnetic ferrite layer is exchange-coupled with the hard ferromagnetic Sm2Fe17N3 particles. In this paper, we provide evidence of exchange coupling in ferrite/Sm2Fe17N3 composites by the following means: 1) measurements of recoil permeability, 2) detailed microstructural observation and 3) calculations of the reduction in remanence due to the introduction of a ferrite layer in the Sm2Fe17N3 magnets. Our ferrite/Sm2Fe17N3 composite magnets are a novel type of spring magnet in which an insulating soft magnetic phase is exchange-coupled with hard magnetic phase.