Small-angle neutron scattering measurements of Neodymium-Iron-Boron (Nd-Fe-B) sintered magnets

Takeda, Masayasu  ; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*

A Neodymium Iron Boron (Nd-Fe-B) sintered magnet is the most powerful permanent magnet among the commercially available ones. Because of the low , the coercivity of this magnet rapidly reduces above the room temperature. It is well known that substitution of dysprosium (Dy) for a part of Nd recovers the coercivity at the high temperatures. There are two key parameters to enhance the coercivity of Nd-Fe-B sintered magnets without the addition of Dy: grain refinement of microstructure in the magnets, and the microstructural control at the interface between NdFeB and Nd-rich phases surrounding the main phase. Small-angle neutron scattering (SANS) is very powerful tool to investigate such internal structures. We performed SANS measurements of the Nd-Fe-B sintered magnets using unpolarized and polarized neutrons on SANS-J-II installed at JRR-3. The information is essential to the achievement of the high-coercivity Dy-free Nd-Fe-B sintered magnet.