Anisotropy of rare-earth magnets

稀土学报(英文版), 2009, 27(4): 675-679. doi: 10.1016/S1002-0721(08)00314-2

^1, , ^2,

1.Department of Physics and Astronomy,NCMN,University of Nebraska,Lincoln,NE 68508,USA

2.Department of Physics and Astronomy,NCMN,University of Nebraska,Lincoln,NE 68508,USA

Anisotropy of rare-earth magnets

R.Skomski ^1, , D.J.Sellmyer ^2,

1.Department of Physics and Astronomy,NCMN,University of Nebraska,Lincoln,NE 68508,USA

2.Department of Physics and Astronomy,NCMN,University of Nebraska,Lincoln,NE 68508,USA

Keywords： magnetic anisotropy

Rare-earth intermetallics such as Nd2FeI4B and Sm-Co are widely used as high-performance permanent magnets,because they combine high magnetocrystalline anisotropy with reasonable magnetization and Curie temperature.The anisotropy is a combined effect of spin-orbit coupling and electrostatic crystal-field interactions.The main contribution comes from the rare-earth 4f electrons,which are well-screened from the crystalline environment but exhibit a strong spin-orbit coupling.In this limit,the magnetocrystalline anisotropy has a very transparent physical interpretation,the anisotropy energy essentially being equal to the energy of Hund's-rules 4f ion in the crystal field.The corresponding expression for the lowest-order uniaxial anisotropy constant K1 is used to discuss rare-earth substitutions,which have recently attracted renewed interest due to shifts in the rare-earth production and demand.Specific phenomena reviewed in this article are the enhancement of the anisotropy of Sm2Fe17 due to interstitial nitrogen,the use of Sm-Co magnets for high-temperature applications,and the comparison of rare-earth single-ion anisotropy with other single-ion and two-ion mechanisms.

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Anisotropy of rare-earth magnets

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