Surface acoustic wave devices (SAW) have a major interest in sensor applications due to their ease of manufacturing, their sensitivity, small size, and wireless structures. Indeed, especially in SAW resonator geometry, the sensor can be wireless addressed and measured with any embedded power. Surface Acoustic Wave sensors have been used to measure a large variety of stimuli like temperature, pressure, constrain [ref]. It is also known that the velocity or resonant frequency of SAW devices including a magnetostrictive material can be changed by applying a magnetic field. By using magnetostrictive single materials or composites with enhanced magnetoelectric coefficients, various magnetic SAW sensors have been proposed during these last ten years. However, their use to sense magnetic fields is restricted to low magnetic fields and the capability to wireless measure bipolar fields and/or high fields is lacking. Furthermore, the occurrence of hysteresis in the SAW response has not been addressed. In this paper, we report magnetic Surface Acoustic Wave (SAW) sensors that consist of interdigital transducers made of a magnetostrictive material (Ni and TbFe2) or based on exchange-biased multilayers (Co/IrMn and CoFe/IrMn). In the SAW resonator geometry, the wireless measure could be performed in a field range depending on the system studied. The intensity and sign of the applied field could be extracted. Finally, the control of the electrode magnetic properties insured reversible behavior in the SAW response.
Vincent Polewczyk, Karine Dumesnil, Daniel Lacour, Mohammed Moutaouekkil, Hamid Mjadeh, Nicolas Tiercelin, Sébastien Petit Watelot, Yannick Dusch, Omar Elmazria, Abdelkrim Talbi, Olivier Bou Matar, and Michel Hehn, "High field bipolar magnetic field sensors based on surface acoustic wave resonators (Conference Presentation)," Proc. SPIE 10357, Spintronics X, 103571U (Presented at SPIE Nanoscience + Engineering: August 09, 2017; Published: 19 September 2017); https://doi.org/10.1117/12.2275731.5581360768001.
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