Shifting the operating frequency of magnetoelectric sensors

Abstract

A method is presented for increasing the operating frequency of symmetric and asymmetric magnetoelectric (ME) sensors so that the operating frequency can be equal to the mechanical resonance frequency of the sensor. This increase improves the signal to noise ratio of a symmetric sensor by at least two orders of magnitude because it mitigates the effect of 1/f noise and the sensor has an increased response at its resonant frequency. The method is based on the strong, nonlinear magnetic field dependence of the magnetostriction. Our method has lowered the detection limit to 4 pT/Hz at 1 Hz in a magnetically unshielded environment.

High non-linear magnetoelectric coefficient in Metglas/PMN-PT laminate composites under zero direct current magnetic bias

“…This results in the mitigation of a strong 1/f noise, which is often quite large at frequencies near or below 1 Hertz (Hz). [4][5][6] A DC magnetic field (H DC ) controlled frequency multiplier/doubling effect has been reported in FeBSiC/PZT 7 and Metglas/PZT 8 ME unimorph structures. Different strengths of the geomagnetic field scalar along three mutually orthogonal directions can serve as an intelligent switch for the control of this frequency multiplication effect.…”

Structural dependence of nonlinear magnetoelectric effect for magnetic field detection by frequency modulation

“…In a magnetically unshielded environment, the sensitivity to small changes in H AC can be enhanced by at least two orders magnitude compared to passive magnetic sensors. 10 However, to date, all investigations of the nonlinear ME coefficient, which is the physical basis of the frequency modulation method, have been reported using the same laminate structure as that used in the passive mode. 11 Due to a dependence of the different orders of nonlinearity on the magnetostrictive material, the structure resulting in a maximum nonlinear ME coefficient may not be the same as for the linear ME effect used in the passive mode.…”

“…The increased background noise by modulation mainly limits the sensitivity. 10 If the undesired background noise could be reduced, the sensitivity could be further enhanced by two orders of magnitudes.…”

“…Recently, ME laminate composites have also been used in an active mode to sense small DC magnetic fields or weak AC magnetic fields, via a frequency modulation technique. 9,10 Such an approach has been utilized to reduce the environmental vibrational noise and 1/f noise in the low frequency range. In a magnetically unshielded environment, the sensitivity to small changes in H AC can be enhanced by at least two orders magnitude compared to passive magnetic sensors.…”

Magnetoelectric laminate sensor system for pico-tesla magnetic field sensing

“…This kind of modulation avoids a strong flicker noise, which often occurs at low frequencies and some vibration noise [Gillette (2011);Petrie (2012);]. This method is called cross-modulation technique.…”