Tayloring the hysteresis loop of soft magnetic nanocrystalline alloys by magnetic and tensile stress annealing

The eddy current limits for metallic cores should be shifted above 1 MHz in order to keep the operating frequencies about 100 to 500 kHz for inductors and transformers. The high operating frequency permits the mass and volume reducing which is a major demand nowadays in aerospace and automobile applications. Specially, in the context of aerospace applications, a magnetic material that can maintain a lower core loss over the applicable temperature range can provide a basis for nosing out the competition with ferrites (limited temperature range) and with crystalline permalloy of 17 μm thick (limited plastic yields strength). It has been recognized that for low loss and wide applicable temperature demand magnetic field and stress annealed Finemet represent an advanced material permitting new solutions for high frequency magnetics. Compact toroids without gap can be prepared with high quality factor and high current inductors. This work presents some new results concerning the magnetic field and stress annealing.