A micromachined silicon magnetometer

A novel magnetic sensor is under investigation. This device is a bidimensional generalization of vibrating reed magnetometers, and is intended to be sensitive to very low magnetic fields (about 10(-13) T Hz(-1/2)) and to very low magnetic moments. This sensor uses the magnetic force which acts on a sample of total magnetization M submitted to a magnetic field gradient gradB. The deformation caused by the force applied to a thin silicon membrane can be capacitively detected. When the field gradient is an alternating one at the resonance frequency of the membrane, the deformation is enhanced by the Q-factor. With such a device, one could perform magnetic measurements with unsurpassed sensitivities over a wide range of temperature. An experimental set-up to perform Q measurements on Si membranes submitted to an alternating electrostatic force is also described.