Improved soft magnetic properties in nanocrystalline FeCuNbSiB Nanophy® cores by intense magnetic field annealing

The effect of high external magnetic field (up to 7 T) on soft magnetic properties in nanocrystalline Fe74.1Si15.7Nb3.1B6.1Cu1 Nanophy® cores has been investigated. The as-quenched amorphous ribbons were nanocrystallized by annealing between 540 and 620 °C in transverse magnetic field. By varying annealing field from 0 to 7 T, induced anisotropy ranging from as low as 4 J/m3 to as high as 41 J/m3 is obtained. It is responsible for an increase in the cut-off frequency up to 300 kHz when the material is submitted to dynamic magnetic excitations. A minimum coercivity of 0.74 A/m is observed in the core annealed in 1 T associated to low losses. The relative permeability decreases on increasing the annealing field intensity with a minimum value of 13,654 at 7 T. Such permeability level opens the way to new applications of the Nanophy® alloys.