Improved pulse carrier MI effect by flash anneal of amorphous wires and FM wireless CMOS IC torque sensor

A figure of merit (FOM) for the magneto-impedance (MI) effect is defined by the product of the MI ratio and the cut-off frequency for ac field detection as (|/spl part/Z//spl part/Hex|/Z/sub 0/)/spl middot/f/sub cutoff/. The FOM for almost zero-magnetostrictive amorphous wire of 30 /spl mu/m diameter was about improved 2.5 times by twisting and flash annealing using a pulse current of 80 mA, 1 second. A sensitive, quick response, and low power consumption wireless FM type MI sensor is constituted using the high FOM amorphous wire head combined with all CMOS IC sensor circuit. The wireless MI sensor is successfully applied to a torque sensor fixed on an automobile power steering steel.