Development of a magnetostrictive Fe₃O₄-film electromagnetic acoustic transducer

The magnetostrictive Fe₃O₄-film electromagnetic acoustic transducer (EMAT) consists of a magnet, a coil, and a magnetostrictive Fe₃O₄-film bonded to a sample, which can be implemented on parts that are complex shaped, or have uneven or rough surfaces. In this short communication, high transduction efficiency of the proposed EMAT is demonstrated, with a signal-to-noise ratio of up to 50.3 dB, which is beneficial for industrial ultrasonic testing. The proposed EMAT is studied under varying bias magnetic fields and dynamic alternating magnetic fields, to improve transduction efficiency by optimizing the transducer design. The experimental results show a significant nonlinear relationship between the amplitude of the received signal and the strength of the bias magnetic field strength. The horizontal and vertical bias magnetic fields corresponding to the maximum amplitude of the received signal are approximately 0.1 T and 0.14 T, respectively. The amplitude of the received signal varies linearly with the strength of the dynamic magnetic field provided by the EMAT. This investigation represents a further development of magnetostrictive film EMATs, and widens the potential for industrial applications.