Alleviating the peritectic phase formation of Mn–Bi hard magnets: Effect of isovalent Sb-doping and prospective short-time thermal-assisted annealing

Binary manganese-bismuthide-based (MnBi) alloys emerge as an exceptional archetype for a promising transition-metal-bearing hard magnet, but the high-quality alloying formation of the ferromagnetic phases is predominantly hindered by the peritectic reaction of transition metal Mn and semimetal Bi during the solidification procedure, as well as usually containing non-magnetic impurities. To alleviate these issues, we employed the well-established bottom-up procedure, including rapid melt-spinning, followed by a thermal crystalline-growth-assisted annealing process, to fabricate high-performance stoichiometric Mn 54 Bi 46 alloying ribbon and its Sb-doped samples. Substituting a small amount (up to 4 at. %) of isovalent configuration (s 2 p 3 ) Sb for Bi in the samples pronounces the particle-size reduction, resulting in a typically positive effect of coercivity force in phase formation as well as fractional enhancement of the ferromagnetic MnBi phases. In particular, the underlying permanent magnetic features, such as coercivity ( H c ) and saturation magnetization ( M s ), reach corresponding values of 14 kOe with 20 emu/g and 10.5 kOe with 52.5 emu/g, with a typical ( B H ) max = 3.9 MGOe for 2 at. % Sb-doping concentration before and after the annealing conditions of 200 °C for 2 h. While magnetocrystalline anisotropy K 1 is a missing piece in previous studies of Sb-doped MnBi materials, by applying the law of approach to saturation magnetization to high-field magnetic data, we obtain K 1 = 0.92–1.1 MJ/m 3 for the 0–3 at. % Sb-doping annealed samples, which overlap with the known value of pristine MnBi alloys.