Effect of Si addition on the magnetic properties of FeNi-based alloys with L10 phase through annealing amorphous precursor

Abstract

As a promising candidate of rare-earth free hard magnetic materials, L1 0 -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 (Fe 50 Ni 50 ) 84−x Si x P 16 (x = 0, 4 at%) and (Fe 50 Ni 50 ) 86−x Si x P 14 (x = 2, 4, 8 at%) alloys. Especially, the effect of Si on the formation of L1 0 phase in annealed FeNi-based alloys was investigated and clarified. It is found Fe 42 Ni 42 P 16 with a much low crystallization temperature could be an appropriate basic amorphous alloy for the formation of L1 0 phase. The addition of Si enhanced the thermal stability of Fe-Ni-P amorphous alloys. Interestingly, Si could stabilize the L1 0 phase in annealed samples and increase its disordering temperature above which L1 0 -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 L1 0 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 L1 0 lattice would be a promising strategy for the massive formation of L1 0 -FeNi like other ordered phases (i.e. L1 2 -FeNi, L1 0 -CoPt), and could substantively contribute to the artificial fabrication of FeNi-based rare-earth free magnets in future. • Sample with the high coercivity above 900 Oe is obtained by annealing Fe-Ni-Si-P amorphous alloy. • The addition of Si increases the crystallization temperatures and thermal stability of Fe-Ni-P amorphous alloys. • Si could enhance the thermal stability and the disordering temperature of L1 0 phase. • Excessive Si addition would deteriorate the intrinsic magnetic hardness of L1 0 phase.