Magnetic properties of 120-mm wide ribbons of high B_s and low core-loss NANOMET® alloy

A 120-mm wide amorphous ribbon of a Fe-Co-Si-B-P-Cu NANOMET® alloy has been successfully produced by a single roll melt spinning technique. The optimally annealed samples exhibited low coercivity (H_c) of 5-7 A/m and high saturation magnetic flux density (B_s) of 1.83 T. The plots of H_c and B_s vs. annealing temperature (T_a) revealed basin-like and plateau-like characteristics, respectively, indicating the good annealing controllability for nanocrystallization and for obtaining soft-magnetic properties with high B_s. The excellent magnetic softness was attributed to the nanocrystalline structure composed of homogeneously dispersed α-Fe grains (with a size of 15-20 nm in diameter) emerged from the amorphous structure after optimum annealing. The nanocrystalline ribbons also exhibited low core-losses (W at 50 Hz) of 0.37 and 0.64 W/kg under maximum flux density of 1.5 T and 1.7 T, respectively. The magnetic properties were comparable with those of laboratory-scale small-width ribbons and confirmed to be independent on the ribbon width, indicating the good reproducibility of this NANOMET® alloy into mass-production-level precursors.