Synthesis and processing effects on magnetic properties in the Fe5SiB2 system

The effects of Ge substitution and synthesis via rapid solidification on the structure and magnetic character of the intermetallic Fe5SiB2 (5-1-2) system were determined, with the objective to investigate the potential of Fe-5(Si0.75Ge0.25)B-2 as a new permanent magnet material. Samples were made by arcmelting/annealing as well as by melt-spinning/annealing and were evaluated by probing the structure, composition, and magnetic response. Results indicate that the tetragonal Cr5B3 crystal structure, large saturation magnetization (Ms = 153.8 emu/g) and Curie temperature (Tc = 784 K) of the parent Fe5SiB2 phase may be preserved by substituting up to 25 at % of Si in the lattice with Ge. The room-temperature magnetocrystalline anisotropy constant of a Ge-substituted alloy of nominal composition Fe-5(Si0.75Ge0.25)B-2 was evaluated as K-1 = 5 x 10(6) ergs/cc using the law of approach to saturation and is the largest reported to date within the 5-1-2 materials system. As a result of compositional modification, the spin reorientation observed in Fe5SiB2 is greatly suppressed from 172 K to 60 K. A comparison of the 5-1-2 phase evolution when synthesized by standard casting and by rapid solidification indicates that melt spinning is a simpler and more expeditious synthesis method relative to previously reported solid-state reaction methods. (C) 2017 Elsevier B.V. All rights reserved.