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First principles calculation of substitutional effects of magnetocrystalline anisotropy in NdFe11Ti and NdFe11TiN

58th Annual Conference on MMM

Yosuke Harashima ( NIMS )
Takashi Miyake ( AIST )
Hiori Kino ( NIMS )
Shoji Ishibashi ( AIST )
Kiyoyuki Terakura ( AIST )

Abstract

The RT12-xMx compounds and their nitrides, having the ThMn12-type structure, are candidate for high-performance permanent magnets, since they contain many iron atoms in the unit cell and can have large magnetization.
However, RFe12 is thermodynamically unstable, and substitution of some of irons by other elements, e.g. titanium is necessary for structural stability.
It is known that interstitial nitrogenation of the neodymium 1-12 type materials exhibits strong uniaxial anisotropy [1].
Substitution and doping elements might be able to control the magnetocrystalline anisotropy but the effects of these elements are still unclear in detail.
We calculated magnetic properties of NdFe12, NdFe11Ti, and those of nitrides using the firstprinciples calculation code QMAS [2] based on density functional theory in the generalized gradient approximation.
In NdFe11Ti and its nitrides, one of the 8i site irons is substituted with the titanium [1].
Strongly localized 4f orbitals are treated as open core states.
The magnetocrystalline anisotropy is estimated from the crystal electric field parameter A20 acting on the neodymium 4f electrons.
We found significant enhancement of A20 parameter by interstitial nitrogenation.
This suggests strong uniaxial magnetic anisotropy and agrees with the experimental results [1].
We also found that the substitution of iron with titanium at the 8i site changes the sign of A20 parameter in NdFe12.
Our new findings indicate the titanium substitution at the 8i site leads to complex magnetic structure.
The part of this work is supported by the Elements Strategy Initiative Center for Magnetic Materials (ESICMM) under the outsourcing project of MEXT, and Future Pioneering Projects / Development of magnetic material technology for high-efficiency motors.
[1] Y. C. Yang, X. D. Zhang, L. S. Kong, Q. Pan, S. L. Ge, Solid State Comm. 78 317 (1991)
[2] http://qmas.jp/


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