Multimode delta-E effect magnetic field sensors with adapted electrodes

Abstract

We present an analytical and experimental study on low-noise piezoelectric thin film resonators that utilize the delta-E effect of a magnetostrictive layer to measure magnetic fields at low frequencies. Calculations from a physical model of the electromechanical resonator enable electrode designs to efficiently operate in the first and second transversal bending modes. As predicted by our calculations, the adapted electrode design improves the sensitivity by a factor of 6 and reduces the dynamic range of the sensor output by 16 dB, which significantly eases the requirements on readout electronics. Magnetic measurements show a bandwidth of 100 Hz at a noise level of about 100 pTHz-0.5

Wide Band Low Noise Love Wave Magnetic Field Sensor System

“…At 10 Hz and 100 Hz equivalent magnetic noise levels of 250 pT/ and 80 pT/ , are achieved, respectively. These values are well within the 100 pT/ range of thin-film ΔE-effect sensors 20 , but the bandwidth is far higher.…”

“…Although it is well known that the relative effects of other elastic moduli such as the shear modulus G are generally more pronounced 17 , most approaches for magnetic sensing have been made using E . The ΔE-effect has been used to detune either cantilever 18 – 20 or bulk resonators 21 coated with a magnetic material. Also, surface acoustic waves (SAWs) have been utilized in resonator or delay line configurations 22 .…”

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

“…14 This has involved research to increase the effect size of the ME response, e.g., materials, effects of device geometry and operation modes, [15][16][17][18] resonance-enhancement and loss mechanisms, 13 and investigation of noise effects and their behavior including the Johnson-Nyquist noise [19][20][21][22][23] from dielectric losses in piezoelectric materials 24 in ME cantilevers and electronics, noise in magnetostrictive (MS) materials, and thermal vibration noise. 23,[25][26][27][28] Different operation modes investigated for low frequency biomagnetic field sensing 14 include (1) direct detection, where magnetic fields oscillating at the cantilever resonance directly excite magnetostrictivepiezoelectric strain coupling and resonance-enhanced signals; (2) modulation techniques, [29][30][31] where signal fields are detected as sidebands to a carrier as a result of frequency mixing in non-linear functional materials; and (3) the ΔE effect, 32,33 where the field dependence of the elastic modulus in magnetostrictive materials is used. Effect size and noise behavior differ greatly with operation mode.…”

Magnetoelastic Effects in Doubly Clamped Electroplated Co77Fe23 Microbeam Resonators

“…There has been a surge of interest in low-power magnetoelectric (ME) magnetic field sensors due to reports of high sensitivity with low noise floors reaching several pT/√ z , [1][2][3][4][5] comparable to fluxgate magnetometers. The basis of the ME sensor relies on the direct strain coupling of piezoelectric and magnetostrictive materials to achieve a magnetic field (H) induced change in the output voltage signal measured across the piezoelectric element.…”