Signal-to-Noise Ratio in Cantilever Magnetoelectric Sensors

Abstract

The signal-to-noise ratio (SNR) is investigated for compound magnetoelectric (ME) sensors on cantilever substrates for detection of low-level magnetic fields. Operated at the mechanical resonance, the magnetic field deforming the magnetostrictive (MS) layer causes a resonant bending mode response in the ME cantilever. The deformation of the piezoelectric (PE) layer allows for extraction of a voltage or charge signal. Here, the influence of the piezoelectric layer thickness and electrode length on the SNR is evaluated in a theoretical study. The signal levels are calculated using the finite element method (FEM). Noise voltages are calculated including the intrinsic electric noise of the ME sensor and amplifier noise for the case of a voltage amplifier and a charge amplifier. AlN and PZT are considered as piezoelectric materials. For a cantilever geometry with 10 mm length, 10 mm width, 300 µm thick silicon substrate, and a Metglas magnetostrictive layer of 2 µm thickness a limit of detection (LOD) in the pT-range is predicted for 2 µm thick AlN layers, while the LOD of PZT ME sensors is approximately one order of magnitude worse. A doubling of the SNR is obtained for choosing an upper electrode covering only the fixed side of the cantilever. Operation with a charge amplifier shows at least ∼50 % better SNR values compared to piezoelectric voltage amplification.Index Terms-Finite element method, magnetoelectric (ME) sensors, magnetic field measurement, magnetostrictive device, noise.

Ultrasensitive Magnetoelectric Sensing System for Pico-Tesla MagnetoMyoGraphy

“…It is noted that assembled sensor arrays are a common method utilized for the vector measurements. State-of-the-art magnetic field sensors based on thin-film ME composites have demonstrated their potential of sub-pT fields detection at room temperature under certain conditions [16], [23], [33]- [36] and with an extremely low magnetic noise level [22]. Still, it is difficult to predict how precisely a sensor behaves when an external magnetic field is applied, especially when the sensor structure comprises several layers of materials.…”

Effect of excitation mode on the magnetic field detection limit of magnetoelectric composite cantilevers

“…Partial electrodes are not considered here. 37 Figures 1(b)-1(g) show magnetoelectric cantilevers excited in different bound-free and freefree modes. At higher modes, strain reversal occurs along the cantilever.…”