Magnetic Field Tunable Ferromagnetic Shape Memory Alloy-Based Piezo-Resonator

Abstract

In this letter, we have performed a comprehensive analysis of the influence of the magnetic field on BAW resonator consisting of a highly magnetostrictive layer and AlN thin film. The fundamental resonant frequency of the fabricated BAW resonator is about ~4.22 GHz. In the presence of a magnetic field, we studied the effect on the resonator parameters such as resonant frequency, acoustic velocity, and coupling coefficient. For the magnetic field of strength 1200 Oe, the resonant frequency significantly shifts by ~360 MHz. Resonant frequency increases and electromechanical coupling coefficient (kt) decreases with the increase in the DC magnetic field. The maximum acoustic velocity of ~7350 m/sec was observed at the magnetic field of 1500 Oe when applied parallel to the surface. Agilent Advanced Design Software (ADS) was used to extract the equivalent Modified Butterworth-Van Dyke circuit parameters (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> , C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> , and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ) of the resonator. Further, in the presence of the magnetic field, we obtained the variation in values of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> , C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> , and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> of the resonator structure. Such tunable resonators can be useful and vital in dealing with varying frequency bands for sustainable growth in wireless communication and magnetic field sensor applications.