Origin of the improved Bs for Fe-Si-B-Mn microalloyed amorphous alloys

In this study, the saturation magnetic flux density (Bs) and the local structure of Fe80Si9-xB11Mnx (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0 at.%) amorphous alloys are investigated. The optimum addition of 0.3 at.% Mn on Bs results from the strengthening of ferromagnetism with larger interatomic distance of Fe. However, excess Mn addition will result in the antiferromagnetic coupling between Mn and Fe atoms, which in turn leads to the decrease of Bs. A model has been proposed to evaluate the optimum doping content of Mn for the highest Bs by calculating the fraction of amorphous pure Fe with average magnetic moment of 0.40 μB and the coordination number of one Mn solute. The present work is promising to provide a guideline for choosing the content of the minor alloying on improving Bs of Fe-Si-B amorphous system.