Mechanism of magnetization reversal of 2∶14∶1 high-entropy rare-earth permanent magnets
Authors: SHI Zhenhua , HU Xinzhe , ZHOU Houbo , TIAN Zhengying , HU Fengxia , CHEN Yunzhong , SUN Zhigang , SHEN Baogen ,   College of Materials Science and Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, China,   State Key Laboratory of Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China,   Shanxi Key Laboratory of Magnetoelectric Functional Materials and Application, Taiyuan University of Science and Technology, Taiyuan 030024, China,   Ganjiang Innovation Academy, Chinese Academy of Sciences, Ganzhou 341000, China,   Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences, Ningbo 315201, China
Published: December 2024

Rare-earth elements share similar ground-state electronic properties, and their unique lanthanide contraction effect can lower the mixing enthalpy of rare-earth elements in high-entropy materials, which is of great significance for fabricating low-cost and high-performance high-entropy rare-earth intermetallic compounds. In this work, the magnetization reversal mechanisms of rapidly quenched ribbons such as Nd<sub>11.76</sub>Fe<sub>82.36</sub>B<sub>5.88</sub> (NdFeB) and the relevant high-entropy rare-earth permanent magnet alloy compounds (La<sub>0.2</sub>Pr<sub>0.2</sub>Nd<sub>0.2</sub>Gd<sub>0.2</sub>Dy<sub>0.2</sub>)<sub>11.76</sub>Fe<sub>82.36</sub>B<sub>5.88</sub> and (La<sub>0.2</sub>Pr<sub>0.2</sub>Nd<sub>0.2</sub>Gd<sub>0.2</sub>Tb<sub>0.2</sub>)<sub>11.76</sub>Fe<sub>82.36</sub>B<sub>5.88</sub> are studied by analyzing the magnetization and demagnetization curves, supplemented by Henkel curves and magnetic viscosity coefficient <i>S</i>. Compared with the pure NdFeB sample, the high-entropy rare-earth permanent magnet has the inter-grain exchange coupling significantly enhanced and the magnetic dipole interaction weakened, indicating that the element diffusion mechanism in heavy rare-earth containing high-entropy material homogenizes the sample, and significantly increases the coercivity. The mechanism of the coercivity is the nucleation of magnetization reversal domains in the grains of the hard magnetic phase. The magnetization mechanism is dominated by pinning at low magnetic fields and by nucleation at high magnetic fields, which is different from the magnetization mechanism of pure NdFeB and has some similarities with the self-pinning mechanism. The magnetic viscosity coefficient of (La<sub>0.2</sub>Pr<sub>0.2</sub>Nd<sub>0.2</sub>Gd<sub>0.2</sub>Dy<sub>0.2</sub>)<sub>11.76</sub>Fe<sub>82.36</sub>B<sub>5.88</sub> is larger than that of pure NdFeB. Due to the asynchrony of hard magnetic phase reversal and intergranular magnetic coupling in (La<sub>0.2</sub>Pr<sub>0.2</sub>Nd<sub>0.2</sub>Gd<sub>0.2</sub>Tb<sub>0.2</sub>)<sub>11.76</sub>Fe<sub>82.36</sub>B<sub>5.88</sub>, the magnetic viscosity coefficient is small but the anisotropy field is large. This indicates that high-entropy sample reduces the magnetocrystalline anisotropy field barrier but increases the magnetocrystalline coupling length. This suggests that the magnetization reversal of high-entropy rare-earth permanent magnet material is significantly different from that of conventional rare earth permanent magnet material and it is worthy of further in-depth research.