SAW magnetic sensors composed of various Ni electrode structures on quartz

A shear horizontal type of surface acoustic wave (SAW) magnetic sensor composed of a Ni electrode of magnetrostrictive metal and an ST-cut 90°X quartz (propagation direction: perpendicular to X-axis) substrate was fabricated. In order to obtain a higher magnetic sensitivity, one-port SAW resonators composed of 3 kinds of Ni electrodes structures on the quartz, such as (a) grooved Ni electrodes, (b) additional overlaid Ni films on grooved Ni electrodes, and (c) Ni electrodes on the quartz, were fabricated. Their sensitivities were almost same, but the SAW resonator composed of (c) structure had highest Q. Using this SAW resonator, a passive, battery-less, and wireless communication system was realized.