Magnetic field response of doubly clamped magnetoelectric microelectromechanical AlN-FeCo resonators

Abstract

Magnetoelectric (ME) cantilever resonators have been successfully employed as magnetic sensors to measure low magnetic fields; however, high relative resolution enabling magnetometry in high magnetic fields is lacking. Here, we present on-chip silicon based ME microelectromechanical (MEMS) doubly clamped resonators which can be utilized as high sensitivity, low power magnetic sensors. The resonator is a fully suspended thin film ME heterostructure composed of an active magnetoelastic layer (Fe0.3Co0.7), which is strain coupled to a piezoelectric signal/excitation layer (AlN). By controlling uniaxial stress arising from the large magnetoelastic properties of magnetostrictive FeCo, a magnetically driven shift of the resonance frequency of the first fundamental flexural mode is observed. The theoretical intrinsic magnetic noise floor of such sensors reaches a minimum value of 35 pT/Hz. This approach shows a magnetic field sensitivity of ∼5 Hz/mT in a bias magnetic field of up to 120 mT. Such sensors have the potential in applications required for enhanced dynamic sensitivity in high-field magnetometry.