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研究活動

Spin-wave dispersion in Nd-Fe-B magnet

The 58th Annual Magnetism and Magnetic Materials (MMM) Conference

Ono, Kanta ( KEK )
Saito, Kotaro ( KEK )
Inami, Nobuhito ( KEK )
Takeichi, Yasuo ( KEK )
Yano, Masao ( TOYOYA )
Shoji, Tetsuya ( TOYOYA )
Manabe, Akira ( TOYOYA )
Kato, Akira ( TOYOYA )
Kaneko, Yuji ( Toyota Central R&D Labs. )
Kawana, Daichi ( ISSP, The University of Tokyo )
Yokoo, Tetsuya ( KEK )
Itoh, Shinichi ( KEK )

Abstract

Spin-wave dispersion in magnetic materials is important since it gives a microscopic viewpoint for the phenomenological magnetic parameters, such as magnetocrystalline anisotropy K1, and exchange stiffness constant A.
Together with the saturation magnetization and the magnetostatic energy, K1 and A determine a wide variety of magnetic properties of magnets such as domain-wall width, domain-wall energy, exchange length, hardness parameter, singledomain radius and anisotropy field.
However, determination of spin-wave dispersion using inelastic neutron scattering is rather difficult for the case of polycrystalline or powder samples.
Neutron Brillouin scattering (NBS) is a promising method to determine spin- wave dispersion for powder samples.
In this study, we tried NBS by using sub-eV pulsed neutrons at High Resolution Chopper Spectrometer (HRC) beamline [1,2] at MLF in J-PARC.
Fig. 1 shows the spin-wave dispersion of Nd-Fe-B strip-cast sample. We observed a clear dispersion of Nd2Fe14B, and found that the result agrees well with with previous results for a single crystal.
The dispersion is fitted with E(q) = E0 + Dsw q2 where E0 is an energy gap at q=0 and Dsw is a spin-wave stiffness constant.
We have obtained E0 = 3.5 meV and Dsw = 82 meVÅ2. K1 and A are determined from E0 and D.
From the spin-wave dispersion measurements, we have determined K1 of 7.57 MJ/m3 and A of 5.4 pm/J which are well consistent with the results from bulk magnetic property measurements.


研究活動

元素戦略拠点

触媒・電池元素戦略拠点
触媒・電池元素戦略研究拠点 (京都大学)
東工大元素戦略拠点
東工大元素戦略拠点 (東京工業大学)
構造材料元素戦略研究拠点
構造材料元素戦略研究拠点 (京都大学)
高効率モーター用磁性材料技術研究組合
高効率モーター用 磁性材料技術研究組合