Magnetic sensor using second harmonic change in magneto-impedance effect

This study reports on a magnetic sensor composed of a Cu wire sandwiched between Go-based amorphous ribbons. The impedance of the Cu wire largely depends on the permeability of the amorphous ribbons and changes with an external field. This phenomenon results in a change in the voltage at the fundamental frequency (V-1st) and that at the second harmonic frequency (V-2nd) at both ends of the Cu wire. The maximum V-2nd variation rate was similar to 150%/Oe which is about 15 times larger than that of V-1st. The detection of the second harmonic voltage offers the potential for a great improvement in the magnetic field sensitivity.