Giant magnetoimpedance in twisted amorphous CoP multilayers electrodeposited onto Cu wires

CoP multilayers grown over Cu wires exhibit magnetoimpedance phenomenon. The change in the real part of the measured voltage is V R = [ V ( H = 0 Oe)- V ( H max )]/ V ( H max ) ≈ 3300%( I rms = 500 mA, 90 kHz); the maximum d V R /d H , is 1280%/Oe at H DC = 1.2 Oe. These quantities are enhanced if the wire is subjected to an angular deformation by means of a torque applied to the wire; V R ≈ 7000% and d V R /d H ≈ 2400%/Oe, are found at 9 and 1.2 Oe, respectively, for a 90° twisted sample, produced by the change in the magnetic anisotropy direction, from the longitudinal to the helical one.