Microstructure and phase dependence of magnetic softness of FeSiGaB nanocrystalline alloys

The effect of annealing on the microstructure and magnetic softness of Fe77.5Si7.5Ga6B9 ribbons has been investigated, and the contribution of Ga addition to the saturation magnetization has been discussed. It was found that as-spun ribbon shown two steps of crystallization processes, which corresponded to the precipitation of alpha-Fe (Ga, Si) and Fe2B. Critical phase separation was detected in the ribbons that prepared at the wheel speed of 25 m/s, which could be due to the heterogenous distribution of Fe and Ga atoms according to X-ray photoelectron spectroscopy results. In addition, Ga in the nearest neighbour position of Fe could improve the magnetic moment mu(Fe), but the participation of Si could diminish the improvement, owing to the free electrons transference between Fe, Ga and Si, and the phase dependence of exchange interacting strength of Fe atoms. Besides, The first principle has a great potential to study the saturation magnetization evolution of Fe-based nanocrystalline alloys.