The effect of current frequency and magnetic field direction in alternative current-field annealing on the GMI and magnetic properties of Co-based wires

• The AC-field Joule annealing on GMI and magnetic properties of CoFeBSi amorphous wire.
• The enhancement of magnetic properties with optimum AC-field annealing.
• In the suitable conditions the GMI and Ms increased from 220% to 400% and 78.5 to 87.2 emu/g respectively.

The effects of applied current annealing frequency, amplitude and magnetic field direction during alternative current-field annealing on giant magnetoimpedance (GMI) and magnetic properties of Co68.15Fe4.35B12.5Si15 wire have been investigated. This annealing process leads to a complex domain structure because of the existence of the variable internal circumferential field and external static magnetic field. We have demonstrated that the applied current annealing with different frequencies, amplitudes and magnetic field directions can improve the magnetic properties and the GMI response. In the as-quenched wire, GMImax and saturation magnetization (Ms) are equal to 220% and 78.5 emu/g respectively. They grow up to 400% and 87.2 emu/g, respectively, while the amplitude of the 50 Hz annealing current is 400 mA and the applied magnetic field, perpendicular to the wire, cancels out the earth's magnetic field. In contrast, the samples annealed by 50 Hz (500 mA) and 100 kHz (400 mA) alternative currents show GMImax = 50% and 140%, and also Ms = 41.8 and 40.7 emu/g, respectively. Altogether, our results show that alternative current-field annealing at appropriate conditions improves the GMI response and makes the samples more suitable for magnetic sensing.