Micromagnetic simulation on magnetic properties of Nd₂Fe₁₄B/α-Fe nanocomposites with Fe nanowires as the soft phase

Abstract

Fe nanowire array with strong shape anisotropy was employed as the soft phase in Nd–Fe–B based nanocomposites. The effects of the Fe nanowire distribution on magnetic properties of the nanocomposites were investigated by micromagnetic simulation. The results indicate that the shape anisotropy of Fe wires added in the same direction as the uniaxial magnetocrystalline anisotropy of the hard phase cannot increase the coercivity of the nanocomposite. When the nanowires are distributed perpendicular to the easy axis of the hard phase, the shape anisotropy of soft phase can retard the moments from rotating to the full reversed direction, leading to enhanced coercivity. In addition, with increasing the nanowire diameter, the coercivity of the nanocomposite decreases, but the dipolar interaction shows different roles in magnetic reversal of nanocomposite for different distributions of nanowires. The current results suggest that the coercivity of the Nd₂Fe₁₄B/α-Fe nanocomposite can be enhanced by introducing the soft magnetic nanowire array with the diameter less than the exchange length and with the long axis along the direction other than the easy axis of hard phase.

Keywords

Nd ₂Fe ₁₄B/α-Fe nanocomposite / micromagnetic simulation / Fe nanowires / shape anisotropy / exchange coupling

References

[1] Coehoorn R, de Mooij D B, de Waard C. Meltspun permanent magnet materials containing Fe₃B as the main phase. Journal of Magnetism and Magnetic Materials, 1989, 80(1): 101–104

[2] Liu Z W, Zhao L Z. Compositional optimization and new processes for nanocrystalline NdFeB-based permanent magnets. In: Advances in Magnetic Materials: Processing, Properties, and Performance. CRC Press, 2017, 293–372

[3] Zhang X Y, Wen G H, Chan Y F, . Fabrication and magnetic properties of ultrathin Fe nanowire arrays. Applied Physics Letters, 2003, 83(16): 3341–3343

[4] Yang S, Zhu H, Yu D, . Preparation and magnetic property of Fe nanowire array. Journal of Magnetism and Magnetic Materials, 2000, 222(1–2): 97–100

[5] Li W, Zhou Q, Zhao L Z, . Micromagnetic simulation of anisotropic grain boundary diffusion for sintered Nd–Fe–B magnets. Journal of Magnetism and Magnetic Materials, 2018, 451: 704–709

[6] Li W, Zhao L Z, Zhou Q, . Effects of grain boundary configuration and characteristics on the demagnetization process and coercivity of anisotropic NdFeB magnets. Computational Materials Science, 2018, 148: 38–45

[7] Fukunaga H, Ikeda M, Inuzuka A. A new type of nanocomposite magnets including elongated soft magnetic grains — computer simulation. Journal of Magnetism and Magnetic Materials, 2007, 310(2): 2581–2583

[8] Aharoni A. Introduction to the Theory of Ferromagnetism. Clarendon Press, 2000

[9] The Object Oriented MicroMagnetic Framework (OOMMF). Available on line: accessed April, 15, 2018)

[10] Kneller E F, Hawig R. The exchange-spring magnet: a new material principle for permanent magnets. IEEE Transactions on Magnetics, 1991, 27(4): 3588

[11] Skomski R, Hadjipanayis G C, Sellmyer D J. Effective demagnetizing factors of complicated particle mixtures. IEEE Transactions on Magnetics, 2007, 43(6): 2956–2958

[12] Hubert A, Schäfer R. Magnetic Domains: The Analysis of Magnetic Microstructures. Springer Science & Business Media, 2008

[13] Schrefl T, Fidler J. Micromagnetic simulation of magnetizability of nanocomposite Nd–Fe–B magnets. Journal of Applied Physics, 1998, 83(11): 6262–6264

[14] Porter D G, Donahue M J. Generalization of a two-dimensional micromagnetic model to non-uniform thickness. Journal of Applied Physics, 2001, 89(11): 7257–7259

[15] Baik J M, Schierhorn M, Moskovits M. Fe nanowires in nanoporous alumina: Geometric effect versus influence of pore walls. The Journal of Physical Chemistry C, 2008, 112(7): 2252–2255

[16] Lu B, Huang M Q, Chen Q, . Magnetic coupling in boron-rich NeFeB nanocomposites. Journal of Applied Physics, 1999, 85(8): 5920–5922

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