Exchange bias phenomena in Pr-doped MnBi magnets at low temperatures

MnBi magnets hold significant potential for the development of high-performance non-rare-earth permanent magnets. The exchange bias phenomenon plays a crucial role in enhancing their coercivity. Pr-doped MnBi alloys exhibits a pronounced exchange bias effect at low temperatures. The exchange bias field initially increases with Pr doping, reaching a maximum of 9.37 kOe, and then decreases at higher doping levels, while the coercivity peaks at 17.59 kOe. The exchange bias field diminishes with rising temperature, applied magnetic field, and repeated magnetic cycling, highlighting its sensitivity to these factors. Micromagnetic simulations reveal that the exchange bias arises from strong interfacial coupling between the ferromagnetic MnBi phase and an amorphous antiferromagnetic phase. The simulations also reproduce the training effect, demonstrating a gradual reduction in net magnetization at the antiferromagnetic interface with repeated cycling. This study advances the understanding of exchange bias phenomena and contributes to the development of high-performance MnBi magnets.