Phase composition and magnetic properties in nanocrystalline permanent magnets based on misch-metal

Highlights: • The magnets were prepared using the misch-metal from Bayan Obo Mine. • Magnetic properties, microstructure and phase composition of misch-metal magnet were surveyed. • The pinning effect of domain wall and the exchange coupling interaction between grains were investigated. • Abnormal R-rich phase composition is necessary to improve magnetic properties in MM-Fe-B magnet. - Abstract: The magnetic properties and phase composition of magnets based on misch-metal (MM) with nominal composition of MM_13+xFe_84−xB_6.5 with x = 0.5, 1, 1.5, 2 and 2.5 using melt-spinning method were investigated. For x = 1.5, it could exhibit best magnetic properties (H_cj = 753.02 kA m⁻¹, (BH)_max = 70.77 kJ m⁻³). X-ray diffraction and energy dispersive spectroscopy show that the multi hard magnetic phase of RE₂Fe₁₄B (RE = La, Ce, Pr, Nd) existed in the magnets. The domain wall pinning effect and the exchange coupling interaction between grains are dependent on the abnormal RE-rich phase composition. Optimizing the phase constitution is necessary to improve magnetic properties in MM-Fe-B magnets for utilizing the rare earth resource in a balanced manner.