An ab-initio theoretical investigation of the soft-magnetic properties of permalloys

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:295

Article

Ostanin, S ; Staunton, JB ; Razee, SSA ; Ginatempo, B ; Bruno, E

关键词: theoretical magnetism;    soft magnets;    permalloys;    Ab-initio electronic structure calculations;   

DOI  :  10.1016/j.jmmm.2005.01.005

来源: Elsevier

【 摘 要 】

We study Ni80Fe20-based permalloys with the relativistic spin-polarized Korringa-Kohn-Rostoker electronic structure method. Treating the compositional disorder with the coherent potential approximation, we investigate how the magnetocrystalline anisotropy, K, and magnetostriction, lambda, of Ni-rich Ni-Fe alloys vary with the addition of small amounts of non-magnetic transition metals, Cu and Mo. From our calculations we follow the trends in K and lambda, and find the compositions of Ni-Fe-Cu and Ni-Fe-Mo where both are near zero. These high permeability compositions of Ni-Fe-Cu and Ni-Fe-Mo match well with those discovered experimentally. We monitor the connection of the magnetic anisotropy with the number of minority spin electrons N-down arrow. By raising N-down arrow via artificially increasing the band-filling of Ni80Fe20 we are able to reproduce the key features that underpin the magnetic softening we find in the ternary alloys. The effect of band-filling on the dependence of magnetocrystalline anisotropy on atomic short-range order in Ni80Fe20 is also studied. Our calculations, based on a static concentration wave theory, indicate that the susceptibility of the high permeability of the Ni-Fe-Cu and Ni-Fe-Mo alloys to their annealing conditions is also strongly dependent on the alloys' compositions. An ideal soft magnet appears from these calculations. (C) 2005 Elsevier B.V. All rights reserved.

【 授权许可】

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