Magnetic sensing by ultrasonic excitation

Magnetic sensing is used for nondestructive evaluation (NDE) of steel products or infrastructures. In this paper, we report a unique magnetic sensing method through the detection of acoustically stimulated electromagnetic (ASEM) response. In this method, magnetization is temporally modulated by ultrasonic irradiation through magnetomechanical coupling of matters, and alternating magnetic fields emitted to surrounding environment are detected by a loop antenna. The magnetic-field dependence of ASEM intensity corresponds to the hysteresis curve of piezomagnetic coefficient in the ultrasonic frequency range. The hysteresis feature of ASEM intensity identifies the presence of thin mill scale with a thickness of 30 μm on the surface of reinforcing steel bars.