Effect of Co addition on hard magnetic properties of annealed Fe-Ni-P amorphous alloys dominated by L10-FeNi phase

Annealing FeNi-based amorphous alloys is a promising way to fabricate rare-earth-free L1(0)-FeNi hard magnetic materials. In this study, the effect of Co addition on the magnetic properties of annealed Fe-Ni-P alloys has been investigated. With Co addition, the coercivity of optimized Fe38Ni38Co8P16 alloys reaches 1145 Oe, which can be attributed to the enhanced magneto-crystalline anisotropy of the L1(0) phase since the remnant coercivity in the out-of-plane direction increases towards 2.35 kOe. By comparing the hysteresis loss and the theoretical magneto-crystalline anisotropic energy of L1(0)-FeNi, the mean volume fraction of L1(0) phase is estimated to be similar to 5.5%. The study suggests that Co addition is greatly beneficial to the fabrication of L1(0)-FeNi hard magnetic materials, and this process has a large potential to be further improved.