Exploring phase formation and magnetic transitions in Sm(Fe1−xMnx)14B by Mössbauer spectroscopy

The Sm2(Fe1−xMnx)14B (0 ≤ x ≤ 0.3) rare earth alloy was prepared by a reduction-diffusion method, and a corresponding reduction-diffusion model was established. The crystal structure, microscopic morphology, and magnetic properties were systematically characterized to investigate the effect of Mn doping. The results show that the diffusion of Sm into FeB proceeded with the formation of the Sm2Fe14B phase from the very beginning of the reaction. Sm2(Fe1−xMnx)14B alloy undergoes a transition from the ferromagnetic phase (x = 0) to the paramagnetic phase (x = 0.2), and the average magnetic moment of Fe decreases from 2.066 to 0.719 µB as observed by 57Fe Mössbauer spectroscopy. In addition, the Curie temperature decreases rapidly from 620 to 230 K. In other words, a wide temperature-regulation of TC can be achieved by adjusting the Mn content, which is attributed to the fact that Mn doping greatly weakens the atomic exchange interactions. These results provide value for potential applications of Re–Fe-based alloys in room temperature magnetic refrigeration.