Influence of cooling rate on structural and magnetic properties of (Fe78Nb8B14)1-xTbx alloys

In the presented work we are focused on the influence of cooling rate on structural and magnetic properties of (Fe78Nb8B14)1-x Tb x (x = 0.08, 0.1, 0.12) nanocrystalline bulk alloys. The samples were fabricated using the vacuum suction technique with different cooling rates controlled by different sample diameters (from 0.5 to 1.5 mm). The increased Nb content leads to the formation of specific microstructure and allows obtaining ultra-high coercive alloys just after casting without any additional treatment. The coercivity exceeds 8.6 T at the room temperature in case of optimal chemical and preparation conditions (x = 0.12, d = 0.5 mm) and 5.6 T for x = 0.1. The impact of Tb content as well as the cooling rate on magnetic and structural (XRD, SEM, MFM) properties is widely discussed in the context of reduction of rare earths in the RE-based permanent magnets.