Crystal Structure and Magnetic Properties of (Fe,Si,Al)-Based Nanocomposite Magnets Designed for Cryogenic Applications

Abstract

In this work, we performed a detailed study of the crystallization, crystal structure, and mag- netic properties of Fe87-zSiz-xAlxNb3B9Cu1 nanocrystalline alloys that were designed primarily for low-temperature applications. In addition, their interesting low-temperature [77 K to 300 K (-196 °C to 27 °C)] magnetic properties (Hc and Ms) were also investigated. These alloys were produced by annealing their amorphous precursors at 823 K (550 °C). Si and Al substitution do not seem to alter the crystallization procedure and crystal structure of the parent alloy but reduces the lattice parameter, the Curie temperature, and the saturation magnetization. On the other hand, it improves the room temperature coercivity at small amounts (Hc = 0.35 A/m for x = 3.5, z = 19) and changes its temperature dependence. As a result, a remarkably low Hc value at 77 K (-196 °C) of 0.45 A/m was observed for x = 6 and z = 23.5.