An ultra-sensitive spintronic strain-gauge sensor with gauge factor of 5000 and demonstration of a Spin-MEMS Microphone

Here we report the first spintronic strain-gauge sensor (Spin-SGS) based on a magnetic tunnel junction (MTJ) with a high gauge factor in excess of 5000, which was realized by adopting a novel amorphous Fe-B-based sensing layer with high magnetostriction and low coercivity in a high magnetoresistance MgO barrier MTJ. We also demonstrate a novel "Spintronic MEMS (Spin-MEMS) microphone," in which a series of Spin-SGSs are integrated onto a bulk micromachined diaphragm. The Spin-MEMS microphone exhibits a signal-to-noise ratio (SNR) of 57 dB(A) due to the high strain sensitivity of the Spin-SGSs. Furthermore a Spin-MEMS microphone with a first resonance frequency of 74 kHz is also fabricated that exhibits an SNR of 45 dB(A). This demonstrates the feasibility of Spin-SGSs in highly sensitive MEMS sensor applications.