An ultrasensitive spintronic strain‐gauge sensor and a spin‐MEMS microphone

Abstract

This review provides the 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 Mg‐O barrier MTJ. This review also provides a demonstration of 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.