Coil-less fluxgate effect in amorphous wires

In this study, the coil-less fluxgate properties of as-received amorphous microwires with the compositions (Co0.94Fe0.06)72.5Si12.5B15, Fe77.5Si7.5B15 and Co72.5Si12.5B15 have been investigated. As its name implies, a coil-less fluxgate is a new type of magnetic field sensor without a coil. When the (Co0.94Fe0.06)72.5Si12.5B15 wire is magnetically saturated in the circumferential direction with a 30 kHz and 48 mA driving current and under the effect of 33π rad/m torsional strain, there is a linear variation in the second harmonic of the voltage from wire ends, Uwire, as a function of the applied external dc magnetic field, Hz, along the wire length. The slope of the second harmonic versus Hz curve changes in opposite directions as the direction of torsional strain changes from the positive to the negative direction. Coil-less fluxgate effects in as-received Fe77.5Si7.5B15 and Co72.5Si12.5B15 wires have also been investigated. A very small change in the second harmonic of voltage Uwire is observed in Fe77.5Si7.5B15 wire, with some small hysteresis.