Piezoelectric/magnetostrictive MEMS resonant sensor array for in-plane multi-axis magnetic field detection

This paper reports the demonstration of an array of piezoelectric/magnetostrictive micro electromechanical system (MEMS) magnetic resonant sensors (PM-MRS) for multi-axis magnetic field (H-field) detection. An array of 43 MHz aluminum nitride (AlN) piezoelectric resonators vibrating along different in-plane directions (θ) but coated with a magnetostrictive layer (Fe
_65.6
Co
_9.4
B
₂₅
) with the same easy axis (EZ) exhibit unique mechanical/ electrical responses as a function of the applied H-field and its direction, enabling a high resolution multi-axis H-field detection. The sensor design yields resonators with a high quality factor (Q ~ 1500) and electromechanical coupling coefficient (k
_t
²
~ 2%) - the highest value ever reported for an AlN PM-MRS. This sensor system paves the way for low power magnetometers that enables single-chip multi-axis H-field detection.