DC and AC linear magnetic field sensor based on glass coated amor- phous microwires with Giant Magnetoimpedance

Giant Magnetoimpedance (GMI) effect has been studied in amorphous glass-coated microwires of composition (Fe6Co94)(72.5)Si12.5B15. The impedance of a 1.5 cm length sample has been characterized by using constant AC currents in the range of 400 mu A-4 mA at frequencies from 7 to 15 MHz and DC magnetic fields from -900 to 900 A/m. Double peak responses have been obtained, showing GMI ratios up to 107%. A linear magnetic field sensor for DC and AC field has been designed, using two microwires connected in series with a magnetic bias of 400 A/m with opposite direction in each microwire in order to obtain a linear response from +/- 70 (A/m)(rms) for AC magnetic field, and +/- 100 A/m for DC magnetic field. A closed loop feedback circuit has been implemented to extend the linear range to +/- 1 kA/m for DC magnetic field. (C) 2014 Elsevier B.V. All rights reserved.