Sensing Function in Amorphous Magnetic Materials

Sensor applications of amorphous materials have been diversifying because of the attractive sensing functions afforded by such materials. Among such functions are the quick response of magnetization due to high resistivity, stress sensitivity of magnetic characteristics due to the absence of crystalline anisotropy, and nonlinear magnetic properties controllable by an induced anisotropy. In this article, one such nonlinear characteristic, the "large Barkhausen discontinuity", and a related phenomenon, the "Matteucci effect", in amorphous wires and ribbons are discussed. Because of the low coercivity of domain walls in amorphous materials, a large Barkhausen discontinuity can be introduced easily by inducing a magnetostrictive or ordering anisotropy to raise the nucleation field for reverse domains. These materials exhibit very sharp and stable flux changes in low fields, and generate sharp voltage pulses, enabling applications as sensitive sensor elements for detection of weak magnetic fields.