Detection of the magnetite by giant magnetoimpedance sensor

• The raw magnetite can be sensitively detected by the GMI sensor.
• The impedance was greatly increased due to the longitudinal stray magnetic field.
• Whole decline in GMI ratio was observed in the presence of magnetite on GMI sensor.

Meander-line NiFe/Cu/NiFe films-based giant magnetoimpedance (GMI) sensor was employed to detect raw magnetite aiming to develop a sensitive magnetometer for the exploration of magnetite. The GMI effect was greatly decreased after placing the magnetite on the GMI sensing elements, which was probably related to the transverse magnetization process becoming strongly inhibited by the stray magnetic field. In addition, we observed an interesting phenomenon: the GMI curve on frequency dependency has shifted to a higher frequency when the magnetite was magnetized at the edge of the sensing elements. Significant changes in impedance can also be found when the magnetite was placed at the edge of GMI sensor without using the external magnetic field, demonstrating the possibility of using the GMI sensor for preliminary exploration of magnetic minerals.