picoTesla Magnetoelectric Sensors with Low-Curvature Nano-Plate Resonators

Prior studies have shown the effectiveness of piezoelectric/magnetostrictive MEMS magnetometers featuring a nano plate resonator and using the ΔE effect for highly sensitive detection of DC magnetic fields. By monitoring changes in resonance frequency from applied magnetic fields, a sensitivity of a few Hz/nT has been achieved in unshielded lab environments. With dimensions of ≤ 200 μm across, and < 1 μm thick, these devices offer the advantages of small scale, including portability and low power consumption, as well as high spatial resolution in sensor arrays. However, a thorough understanding of magnetic properties and other performance aspects in these magnetometers has not been developed. In this study we report on the strong effects of resonator plate curvature on sensor performance. It was found that the total resonance frequency shift dropped off exponentially with increasing curvature by as much as two orders of magnitude. By fabricating a ΔE effect magnetometer with low curvature in the nano plate resonator, we achieved maximum magnetic field sensitivity of 4.98 Hz/nT. High frequency stability was also observed: an Allan deviation measurement yielded a minimum of 0.0245 Hz at 100 ms averaging time. This results in a theoretical limit of detection of 1.56 pT/Hz^1/2.