Enhancing the sensitivity of magnetoelectric sensors by increasing the operating frequency

We present a field modulation technique that increases the operating frequency of magnetoelectric ( ME) sensors so that it can match the mechanical resonance frequency of the sensor. This not only improves the sensitivity but also reduces the effect of 1/f noise that is inherent at low frequencies. The technique, which is shown to apply to both symmetric and asymmetric ME sensors, relies on the strong, nonlinear magnetic field dependence of the magnetostriction. The combination of a lower 1/f noise and enhanced response at resonance has increased the signal to noise ratio of a symmetric sensor by two orders of magnitude. The detection limit of this sensor was lowered from 90 to 7 pT/root Hz at 1Hz in a magnetically unshielded environment. (C) 2011 American Institute of Physics. [doi:10.1063/1.3668752]