Microstructure and Magnetic Properties of Mn 55 Bi 45 Powders Obtained by Different Ball Milling Processes

Low-temperature phase (LTP) MnBi is considered as a promising rare-earth-free permanent magnetic material with high coercivity and unique positive temperature coefficient of coercivity. Mn₅₅Bi₄₅ ribbons with high purity of LTP MnBi phase were prepared by melt spinning. Then, Mn₅₅Bi₄₅ powders with different particle size were obtained by low-energy ball milling (LEBM) with and without added surfactant. The coercivity is enhanced in both cases. Microstructure characterization reveals that Mn₅₅Bi₄₅ powders obtained by surfactant assisted low-energy ball milling (SALEBM) have better particle size uniformity and show higher decomposition of LTP MnBi. Coercivity can achieve a value of 17.2 kOe and the saturation magnetization (<i>M</i>_s) is 16 emu/g when Mn₅₅Bi₄₅ powders milled about 10 h by SALEBM. Coercivity has achieved a maximum value of 18.2 kOe at room temperature, and 23.5 kOe at 380 K after 14 h of LEBM. Furthermore, Mn₅₅Bi₄₅ powders obtained by LEBM have better magnetic properties.

Abstract licence: CC BY

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