Structure and Magnetic Properties of a Fe_73.5Si_13.5B₉Nb₃Cu₁Alloy Nanopowder Fabricated by a Chemical Etching Method and Milling Procedure

The magnetic and structural properties of FINEMET (the Hitachi product name of the Fe-Si-B-Nb-Cu alloy) nanopowder with a composition of $Fe_73.5Si_13.5B_9Nb_3Cu_1$ atomic percent were investigated after annealing, chemical etching, and mechanical milling. The primary and secondary crystallization temperatures were 523 and $550^\circC$, respectively. The grain size of the particles was adjusted by annealing time. Optimally annealed particles exhibited a homogenous microstructure composed of nanometer-sized crystalline grains. The grain boundary of the annealed particles was etched preferentially by chemical etching. Chemically etched particles were broken at the grain boundary by high-energy ball milling. As a result, a nanometer-sized FINEMET powder with a uniform size of crystalline grains was fabricated.