Stress sensitivity and nanocrystalline phase evolution in FINEMET-type alloys

The frequency dependence of permeability change due to 1% mechanical deformation is investigated in FINEMET-type soft magnetic cores after various degree of amorphous-nanocrystalline transformation. It was found that stress sensitivity is especially high at the early stage of nanograin formation, and gradually decreases as the Si-content of the nanograin assembly increases. The permeability changes are correlated with TEM and X-ray diffraction results.