Microstructure and magnetic properties of Sm3Co11−xFexB4 ribbons with superior coercivity

This paper reports the relationship between the microstructure and magnetic properties of a new Sm3Co11B4-type alloy with ultra-high coercivity. Sm3Co11−xFexB4 (x = 0, 0.5 and 1.0) ribbons were prepared by melt-spinning at 30 m/s and then annealing at 800 °C for 30 min. The microstructural analysis demonstrates that the x = 0 ribbons consist of equiaxed Sm3Co11B4, Sm5Co19B6, Sm2Co7B3, and SmCo4B grains. A small amount of Fe addition does not change the phase composition but transforms the microstructure into a strip-like morphology in x = 0.5 ribbons, which increased both the coercivity and magnetization and obtained a quite high coercivity of 4.7 MA/m. When Fe content increases to x = 1.0, a new SmCo12B6-type phase forms, and the microstructure is converted from strip-shaped to equiaxed morphology, which reduces the coercivity due to the non-magnetic characteristic of SmCo12B6 and the increase of effective demagnetization field. The underlying mechanism was revealed by microstructure evolution in connection with the magnetic properties.