(ESICMM-G8 Symposium on Next Generation Permanent Magnets, Tsukuba, 2015)
Magnetic interactions between nanocrystalline grains in Nd-Fe-B hot-deformed magnets


Kanta Ono (KEK), Masao Yano (TOYOTA Motor Co.), Tetsuro Ueno (ESICMM, NIMS), Kotaro Saito (KEK), Tetsuya Shoji (TOYOTA Motor Co.), Noritsugu Sakuma (TOYOTA Motor Co.), Akira Manabe (TOYOTA Motor Co.), Akira Kato(TOYOTA Motor Co.)

Abstract:

  High coercivity mechanism in Nd-Fe-B magnet is important towards the realization of Dy-free high coercivity permanent magnets. Recent progress is Nd-Fe-B nanocrystalline hot-deformed magnet with an infiltration of Nd-Cu eutectic alloys, which enhances coercivity [1]. In Nd-Fe-B nanocrystalline magnets, grain boundaries plays an essential role in decreasing exchange interactions, and it is suggested that magnetic dipolar interaction becomes important. The significance of magnetic interactions between grains in magnetization reversal process is not well understood, since quantitative measurement of the magnetic interactions in magnetic materials is rather difficult.
  In this study, we have developed a quantitative visualization method for the dipolar energy and exchange energy distributions in Nd-Fe-B nanocrystalline magnets with and without Nd-Cu infiltration process using scanning transmission x-ray microscopy (STXM) [2-4] and large-scale micromagnetic simulation. We have also performed small-angle neutron scattering (SANS) for bulk Nd-Fe-B nanocrystalline magnets to analyze the magnetic interactions between grains [5-7]
  Fig.1 shows the dipolar energy distribution of Nd-Fe-B nanocrystalline magnet without and with Nd-Cu infiltration process taken after applied magnetic field of 0 and -10 kOe. In Nd-Cu infiltrated magnets change in dipolar energy is smaller compare to as deformed magnet. This work was partly supported by ESICMM under the outsourcing project of the MEXT, Japan and was partly supported by the JST under Collaborative Research Based on Industrial Demand“High Performance Magnets: Towards Innovative Development of Next Generation Magnets.” Sample preparation was partly performed under the future pioneering program“Development of magnetic material technology for high-efficiency motors” commissionedby the New Energy and Industrial Technology Development Organization (NEDO).
References
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