Magnetic field microscope using high-sensitivity giant magneto-resistance sensor with AC field modulation

A new high-sensitivity giant magneto-resistance (GMR) sensor system was developed and applied to a magnetic field microscope for which a magneto-impedance (MI) sensor was used as a high-sensitivity magnetic probe. The GMR sensor system achieved a detectivity of 13 pT/root Hz at 100 Hz. The sensing limit and spatial resolution were examined compared with the MI sensor. A 100 Hz AC magnetic field from a patterned Cu line was imaged. The GMR sensor showed better spatial resolution than that of the MI sensor owing to its small sensor unit size. The sensing limit was the same for both the GMR sensor and the MI sensor. This limit is due to ambient magnetic field noise. The GMR sensor could reduce this noise by differential detection using two sensor units. These results suggest that the GMR sensor system has advantages for application to the magnetic field microscopes compared with the MI sensor.

Automated summary

A new high-sensitivity giant magneto-resistance (GMR) sensor system was developed and applied to a magnetic field microscope. Compared with the magneto-impedance (MI) sensor, the GMR sensor system showed better spatial resolution but the same sensing limit. By differential detection, the GMR sensor could reduce ambient magnetic field noise.