Direct integration of magnetoelectric sensors with microelectronics - Improved field sensitivity, signal-to-noise ratio and frequency response

The large magnetoelectric (ME) coupling in the ME laminates makes them attractive for ultrasensitive room temperature magnetic sensors. Here we investigate the field sensitivity and signal-to-noise ratio (SNR) of ME laminates, consisting of magnetostrictive and piezoelectric layers (Metglas and piezopolymer PVDF were used as the model system), which are directly integrated with two different modes of low noise readout circuits - charge mode and voltage mode. For the sensor system with charge mode readout circuit, both the theoretical analysis and experimental results show that increasing the number of piezolayer layers can improve the SNR, especially at low frequencies. We also introduce a figure of merit to measure the overall influence of the piezolayer properties on the SNR and show that the newly developed piezoelectric single crystals of PMN-PT and PZN-PT have the promise to achieve a very high SNR and consequently ultra-high sensitivity room temperature magnetic sensors. The results show that the ME coefficients used in early ME composites development works may not be relevant to the SNR. The results also show that enhancing the piezomagnetic coefficient, for example, by employing the flux concentration effect, can lead to enhanced SNR. For the sensor system in-package with voltage mode readout circuits, both theories and experiments show that the system in package exhibits frequency independent field sensitivity at the whole frequency range of interests. The package ME sensors investigated here show the potential of chip scale ME magnetic sensors with high SNR and sensitivity.