Magneto-Impedance Element Using Amorphous Micro Wire

A large magneto-impedance (MI) effect was found in amorphous magnetic wires while passing a high-frequency current. The amplitude of the induced voltage between the ends of a wire changes by 40 to 50% when an external magnetic field of about 10 Oe (approximately 800 A/m) is applied parallel to the wire axis. This paper reports the principles and basic properties of the MI effect in very small amorphous wires of composition (Fe0.06Co0.94)72.5Si12.5B15 and magnetostriction ¿10^¿7, and describes an application to rotary encoder heads using very small MI elements 30 ¿m in diameter and 1 mm in length.