Effect of Si Addition on the Magnetic Properties of Feni-Based Alloys with L10 Phase Through Annealing Amorphous Precursor

As a promising candidate of rare-earth free hard magnetic materials, L10-FeNi has been paid much attention in the last decades. However, it is difficult to be artificially fabricated due to its low thermal stability and sluggish diffusion ability of atoms below the crucial temperature of 320 °C. In this study, a promising method of annealing amorphous precursor was extensively developed through (Fe50Ni50)84−xSixP16 (x = 0, 4 at%) and (Fe50Ni50)86−xSixP14 (x = 2, 4, 8 at%) alloys. Especially, the effect of Si on the formation of L10 phase in annealed FeNi-based alloys was investigated and clarified. It is found Fe42Ni42P16 with a much low crystallization temperature could be an appropriate basic amorphous alloy for the formation of L10 phase. The addition of Si enhanced the thermal stability of Fe-Ni-P amorphous alloys. Interestingly, Si could stabilize the L10 phase in annealed samples and increase its disordering temperature above which L10-FeNi phase could deteriorate into soft magnetic phase. As expected, appropriate Si addition indeed improved the hard magnetic properties of the annealed alloys and samples with high coercivity above 900 Oe was obtained. Further Si addition would deteriorate the magnetic-crystalline anisotropy of L10 phase and decrease the coercivity of annealed Fe-Ni-Si-P alloys. Nevertheless, the results indicate that increasing the order-disorder transition temperature through element doping in L10 lattice would be a promising strategy for the massive formation of L10-FeNi like other ordered phases (i.e. L12-FeNi, L10-CoPt), and could substantively contribute to the artificial fabrication of FeNi-based rare-earth free magnets in future.