中国物理B ›› 2018, Vol. 27 ›› Issue (11): 117503-117503.doi: 10.1088/1674-1056/27/11/117503

所属专题: TOPICAL REVIEW — Magnetism, magnetic materials, and interdisciplinary research

• TOPICAL REVIEW—Magnetism, magnetic materials, and interdisciplinary research • 上一篇    下一篇

Mn-based permanent magnets

Jinbo Yang(杨金波), Wenyun Yang(杨文云), Zhuyin Shao(邵珠印), Dong Liang(梁栋), Hui Zhao(赵辉), Yuanhua Xia(夏元华), Yunbo Yang(杨云波)   

  1. 1 State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China;
    2 Collaborative Innovation Center of Quantum Matter, Beijing 100871, China;
    3 Beijing Key Laboratory for Magnetoelectric Materials and Devices, Beijing 100871, China;
    4 Institutes of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999, China
  • 收稿日期:2018-09-23 修回日期:2018-10-25 出版日期:2018-11-05 发布日期:2018-11-05
  • 通讯作者: Jinbo Yang E-mail:jbyang@pku.edu.cn
  • 基金资助:

    Project supported by the National Natural Science Foundation of China (Grant Nos. 51731001, 11805006, 51371009, 11504348, and 11675006) and the National Key Research and Development Program of China (Grant Nos. 2016YFB0700901, 2017YFA0401502, and 2017YFA0206303).

Mn-based permanent magnets

Jinbo Yang(杨金波)1,2,3, Wenyun Yang(杨文云)1,2,3, Zhuyin Shao(邵珠印)1,2,3, Dong Liang(梁栋)1,2,3, Hui Zhao(赵辉)1,2,3, Yuanhua Xia(夏元华)4, Yunbo Yang(杨云波)1   

  1. 1 State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China;
    2 Collaborative Innovation Center of Quantum Matter, Beijing 100871, China;
    3 Beijing Key Laboratory for Magnetoelectric Materials and Devices, Beijing 100871, China;
    4 Institutes of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999, China
  • Received:2018-09-23 Revised:2018-10-25 Online:2018-11-05 Published:2018-11-05
  • Contact: Jinbo Yang E-mail:jbyang@pku.edu.cn
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Grant Nos. 51731001, 11805006, 51371009, 11504348, and 11675006) and the National Key Research and Development Program of China (Grant Nos. 2016YFB0700901, 2017YFA0401502, and 2017YFA0206303).

摘要:

Mn-based intermetallic compounds have attracted much attention due to their fascinating structural and physical properties, especially their interesting hard magnetic properties. In this paper, we have summarized the magnetic and structural properties of Mn-based intermetallic compounds (MnX, where X=Al, Bi, and Ga). Various methods for synthesizing single phases of MnAl, MnBi, and MnxGa were developed in our lab. A very high saturation magnetization of 125 emu/g, coercivity of 5 kOe, and maximum energy product (BH)max of 3.1 MG·Oe were achieved at room temperature for the pure τ-Mn-Al magnetic phase without carbon doping and the extrusion process. Low temperature phase (LTP) MnBi with a purity above 95 wt.% can be synthesized. An abnormal temperature coefficient of the coercivity was observed for the LTP MnBi magnet. Its coercivity increased with temperature from 100 K to 540 K, reached a maximum of 2.5 T at about 540 K, and then decreased slowly to 1.8 T at 610 K. The positive temperature coefficient of the coercivity is related to the evolution of the structure and magnetocrystalline anisotropy field of the LTP MnBi phase with temperature. The LTP MnBi bonded magnets show maximum energy products (BH)max of 8.9 MG·Oe (70 kJ/m3) and 5.0 MG·Oe (40 kJ/m3) at room temperature and 400 K, respectively. Ferrimagnetic MnxGa phases with L10 structures (x < 2.0) and D022 structures (x > 2.0) were obtained. All of the above structures can be described by a D022 supercell model in which 2a-Ga and 2b-Mn are simultaneously substituted. The tetragonal D022 phases of the MnxGa show high coercivities ranging from 7.2 kOe for low Mn content x=1.8 to 18.2 kOe for high Mn content x=3 at room temperature. The Mn1.2Ga sample exhibits a room temperature magnetization value of 80 emu/g. The hard magnetic properties of coercivity iHc=3.5 kOe, remanence Mr=43.6 emu/g, and (BH)max=2.5 MG·Oe were obtained at room temperature. Based on the above studies, we believe that Mn-based magnetic materials could be promising candidates for rare earth free permanent magnets exhibiting a high Curie temperature, high magnetocrystalline anisotropy, and very high coercivity.

关键词: permanent magnetic materials, magnetic properties, manganese alloys, magnetic structure, coercivity, magnetization, neutron diffraction

Abstract:

Mn-based intermetallic compounds have attracted much attention due to their fascinating structural and physical properties, especially their interesting hard magnetic properties. In this paper, we have summarized the magnetic and structural properties of Mn-based intermetallic compounds (MnX, where X=Al, Bi, and Ga). Various methods for synthesizing single phases of MnAl, MnBi, and MnxGa were developed in our lab. A very high saturation magnetization of 125 emu/g, coercivity of 5 kOe, and maximum energy product (BH)max of 3.1 MG·Oe were achieved at room temperature for the pure τ-Mn-Al magnetic phase without carbon doping and the extrusion process. Low temperature phase (LTP) MnBi with a purity above 95 wt.% can be synthesized. An abnormal temperature coefficient of the coercivity was observed for the LTP MnBi magnet. Its coercivity increased with temperature from 100 K to 540 K, reached a maximum of 2.5 T at about 540 K, and then decreased slowly to 1.8 T at 610 K. The positive temperature coefficient of the coercivity is related to the evolution of the structure and magnetocrystalline anisotropy field of the LTP MnBi phase with temperature. The LTP MnBi bonded magnets show maximum energy products (BH)max of 8.9 MG·Oe (70 kJ/m3) and 5.0 MG·Oe (40 kJ/m3) at room temperature and 400 K, respectively. Ferrimagnetic MnxGa phases with L10 structures (x < 2.0) and D022 structures (x > 2.0) were obtained. All of the above structures can be described by a D022 supercell model in which 2a-Ga and 2b-Mn are simultaneously substituted. The tetragonal D022 phases of the MnxGa show high coercivities ranging from 7.2 kOe for low Mn content x=1.8 to 18.2 kOe for high Mn content x=3 at room temperature. The Mn1.2Ga sample exhibits a room temperature magnetization value of 80 emu/g. The hard magnetic properties of coercivity iHc=3.5 kOe, remanence Mr=43.6 emu/g, and (BH)max=2.5 MG·Oe were obtained at room temperature. Based on the above studies, we believe that Mn-based magnetic materials could be promising candidates for rare earth free permanent magnets exhibiting a high Curie temperature, high magnetocrystalline anisotropy, and very high coercivity.

Key words: permanent magnetic materials, magnetic properties, manganese alloys, magnetic structure, coercivity, magnetization, neutron diffraction

中图分类号:  (Permanent magnets)

  • 75.50.Ww
75.60.-d (Domain effects, magnetization curves, and hysteresis) 75.75.-c (Magnetic properties of nanostructures) 61.05.F- (Neutron diffraction and scattering)