Magnetoresistance based resonance monitoring with pulse-excited planar coils

Magnetoresistance sensing is an attractive resonance monitoring technique for micro/nano-electromechanical systems, due to its merits of simplicity, effectiveness, and independence of capacitance and stress. Nevertheless, the previous schemes suffer from the uncertain magnetic disturbances. In this letter, current pulse based magnetoresistance sensing is proposed to resist this uncertainty. By energizing a pair of planar coils with current pulses, the magnetic disturbances correlated in time can be identified and eliminated in pulse intervals. The detection sensitivity is tunable by varying with the intensity of the pulsed current. Presently, an amplitude detection limit of 0.1 nm/√Hz has been achieved.