The present disclosure provides a micro device. The device has a micro-electro-mechanical systems (MEMS) movable structure, a plurality of metal loops over the MEMS movable structure, and a piezoelectric element over the MEMS movable structure. Frontside and backside capping wafers are bonded to the MEMS structure, with the frontside and backside capping wafers encapsulating the MEMS movable structure, the plurality of metal loops, and the piezoelectric element. The device further includes a magnet disposed on the frontside capping wafer over the plurality of metal loops.