Title: Fabrication of Mn-(Bi, Ga) based hard magnetic nanocomposites

Authors: Nguyen Huy Dan; Pham Thi Thanh; Nguyen Huy Ngoc; Nguyen Hai Yen; Tran Dang Thanh; Jung-Goo Lee; Nguyen Mau Lam; Dinh Thi Kim Oanh

Addresses: Institute of Materials Science, Vietnam Academy of Science and Technology, Graduate University of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, 10000, Vietnam ' Institute of Materials Science, Vietnam Academy of Science and Technology, Graduate University of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, 10000, Vietnam ' Institute of Materials Science, Vietnam Academy of Science and Technology, Graduate University of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, 10000, Vietnam ' Institute of Materials Science, Vietnam Academy of Science and Technology, Graduate University of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, 10000, Vietnam ' Institute of Materials Science, Vietnam Academy of Science and Technology, Graduate University of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, 10000, Vietnam ' Korea Institute of Materials Science, 797 Changwondaero, Seongsan-gu, Changwon, Gyeongnam, 51508, South Korea ' Department of Physics, Hanoi Pedagogical University No. 2, Xuan Hoa, Vinh Phuc, 1500, Vietnam ' Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Vietnam

Abstract: The hard and soft magnetic nanoparticles of Mn-(Bi, Ga) and Fe-Co, respectively, were prepared by using a high energy ball milling method. These nanoparticles were then mixed together with different ratios and subsequently annealed in various conditions of temperature and time to make nanocomposite magnets. The coercivity H_c and maximum energy product (BH)_max of these magnets depend on the nanoparticle size and on the ratio of the hard/soft magnetic phases. The annealing process plays an important role for exchangecoupling between the hard and soft magnetic phases. With sizes in a range of 40-60 nm, the Mn-(Bi,Ga) nanoparticles reveal high coercivity (H_c > 12 kOe) to be a potential rare-earth-free hard magnetic phase for producing nanocomposite magnets. Quite high coercivities, H_c > 4 kOe, and maximum energy products, (BH)_max > 4 MGOe, have been achieved for this kind of rare-earth-free nanocomposite magnets.

Keywords: magnetic nanoparticles; hard magnetic materials; permanent magnets; nanocomposite magnets; rare-earth-free magnets; high coercivity; high energy ball milling method.

DOI: 10.1504/IJNT.2020.111323

International Journal of Nanotechnology, 2020 Vol.17 No.7/8/9/10, pp.529 - 540

Published online: 20 Nov 2020 *

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