Magnetic Properties and Coercivity Mechanism of Nanocrystalline Rare-Earth-Free Co74Zr16Mo4Si3B3 Alloys

The microstructure and magnetic properties of rare-earth-free, melt-spun Co74Zr16Mo4Si3B3 alloys were investigated to enhance their hard magnetic response and elucidate their coercivity mechanism. The alloys exhibit a polycrystalline microstructure composed of randomly oriented, equiaxed grains, predominantly comprising the rhombohedral hard magnetic Co11Zr2 phase (92.4 wt.%). These materials display a favorable combination of magnetic properties, with coercive fields up to 581 kA/m, maximum magnetization reaching 0.30 T, and Curie temperatures as high as 751 K. An interpretation of the results, based on microstructural features, intrinsic magnetic parameters, and micromagnetic simulations, indicates that the coercivity mechanism of these melt-spun alloys can be attributed to the nucleation of reverse magnetic domains.