High sensitivity measurement of magnetic fields using microcantilevers

We have mounted magnetic γ−Fe2O3 particles on the end of a microcantilever in order to make a high sensitivity magnetic field sensor. An externally applied magnetic field exerts a torque on the acicular oxide particles which in turn deflects the cantilever. The deflection is measured using a sensitive optical detection system. We show how the effect of drift in the optical signal can be eliminated by continuously flipping the magnetization direction within the oxide by applying short, intense pulses of magnetic field. The sensor can resolve changes in applied field as small as 10−4 G (10 nT), and has good linearity over five orders of magnitude of applied field strength.

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