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In this paper, we describe a new type of magnetic surface acoustic wave (SAW) sensor that consists of interdigital transducers made of a magnetostrictive material, Ni, on a quartz substrate. This sensor can be used as an element of a resonator-type wireless SAW sensor system because it has a high Q. Moreover, it has the merits of being fabricated easily using the existing process for SAW devices because its structure is the same as that of general SAW resonators. When an external magnetic field of about 100 mT was applied perpendicularly to the direction of SAW propagation, the frequency change obtained was 200 ppm. In addition, the developed sensor was applied in a passive and wireless open/close sensing system and the reading distance obtained was 3 m.

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A shear horizontal type of surface acoustic wave (SAW) magnetic sensor composed of a magnetostrictive Ni electrode and an ST-cut 90 X quartz substrate was fabricated. In this study, in order to obtain a higher magnetic sensitivity, one-port SAW resonators composed of three kinds of Ni electrode structures on the ST-cut 90 X quartz, namely, (a) grooved Ni electrodes, (b) additional overlaid Ni films on grooved Ni electrodes, and (c) Ni electrodes on the quartz, were fabricated and measured. In addition to these, a SAW resonator composed of a magnetostrictive TbFe 2 film electrode, which has a larger magnetostrictivity than the Ni film, on the ST-cut 90 X quartz was also fabricated. Their characteristics are examined. #

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