Development of a passive and remote magnetic microsensor with thin-film giant magnetoimpedance element and surface acoustic wave transponder

Abstract

This paper presents the development of a wireless magnetic field sensor consisting of a three-layer thin-film giant magnetoimpedance sensor and a surface acoustic wave device on one substrate. The goal of this integration is a passive and remotely interrogated sensor that can be easily mass fabricated using standard microfabrication tools. The design parameters, fabrication process, and a model of the integrated sensor are presented together with experimental results of the sensor.

Surface-Acoustic-Wave Induced Ferromagnetic Resonance in Fe Thin Films and Magnetic Field Sensing

“…Like MR-based devices, such magnetic SAW devices are sensitive to the direction and the magnitude of an external magnetic field. SAWs can also be used to develop wireless magnetic field sensors based on coupling a SAW transponder to a giant-magnetoresistance element [3,4].…”

Integration of thin film giant magnetoimpedance sensor and surface acoustic wave transponder

“…Details on the SAW design can be found elsewhere. 23 The distances between IDTs were 5000 lm (from IDT1 to IDT2) and 2500 lm (from IDT2 to IDT3). Since the wave velocity is 3994 m/s for LiNbO 3, the time the wave requires to travel from IDT1 to IDT2 is Dt 1,2 ¼ 1.25 ls and from IDT2 to IDT3 Dt 2,3 ¼ 0.625 ls.…”

Surface Acoustic Wave Based Magnetic Sensors

“…As the water level changes, the resistance between the rods changes, which can be detected as a magnitude and phase change of the signal reflected from the load IDT [27]. Another example for a load is a giant magnetoimpedance sensor [16,17]. A change in the magnetic field yields a change in the sensor's impedance.…”

“…This makes it a suitable load for a SAW transponder, which converts this impedance change into a magnitude and phase change of the reflected acoustic waves. In order to reduce the size and improve the level of integration of the senor, a new design of an integrated SAW transponder and thin film GMI sensor has been proposed and developed recently by the authors [17,18]. The SAW transponder and GMI thin film were integrated on the same chip using standard micro-fabrication technology suitable for mass fabrication.…”