Sensors and Actuators, A: Physical

Microfabricated ultrasensitive piezoresistive cantilevers for torque magnetometry

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New types of piezoresistive cantilevers for torque magnetometry have been microfabricated and tested. The design is optimized to detect the flexion and torsion of the cantilever corresponding to a torque in two directions, which is induced by a microscopic magnetic sample mounted on the lever surrounded by an external magnetic field. The high sensitivity (up to ≈10-14 N m) of the device is achieved by its special geometrical design featuring cantilever legs with only 3-μm-wide beams. The microfabrication process makes use of silicon-on-insulator wafers for precise etch-stop of a novel deep-trench etch process from the backside to fabricate the individual chips. One cantilever version has an integrated metal loop for absolute calibration of the sensor within 1%. The loop can also be used to actuate the lever mechanically. Owing to their small dimension and mass, the new devices feature ultrahigh sensitivity combined with short response time, which allows the characterization of microscopic magnetic samples with very high resolution.