Abstract
This chapter discusses electromagnetic acoustic transducers (EMATs), which produce ultrasonic waves without any coupling medium, in the surface of an electrically conductive material. In Section 2.1 the difference between piezoelectric and electromagnetic generation and reception of ultrasonic waves is described. Section 2.2 presents the mechanisms acting mainly during ultrasound excitation by EMATs, the Lorentz force and magnetostriction. Section 2.3 considers EMATs based on the Lorentz force and Section 2.4 looks at transducers using magnetostriction. Typical arrangements of RF coils and magnets are shown. Directivity patterns are presented. Methods for varying the beam angle are explained. Applications of EMATs are described.
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