Tunneling Magnetoresistance Transition and Highly Sensitive Pressure Sensors Based on Magnetic Tunnel Junctions with a Black Phosphorus Barrier.

Black phosphorus is a promising material to serve as a barrier for magnetic tunnel junctions (MTJs) due to weak van der Waals interlayer interactions. In particular, the special band features of black phosphorus may endow intriguing physical characteristics. Here we study theoretically the effect of band gap tunability of black phosphorus on the MTJs with the black phosphorus barrier. It is found that the tunneling magnetoresistance (TMR) may transition from a finite value to infinity owing to the variation in the band gap of black phosphorus. Combined with the latest experimental results of the pressure-induced band gap tunability, we further investigate the pressure effect of TMR in the MTJs with a black phosphorus barrier. The calculations show that the pressure sensitivity can be quite high under appropriate parameters. Physically, the high sensitivity originates from the TMR transition phenomenon. To take advantage of the high pressure sensitivity, we propose and design a detailed structure of highly sensitive pressure sensors based on MTJs with a black phosphorus barrier, whose working mechanism is basically different from that of convential pressure sensors. The present pressure sensors possess four advantages and benifits: (1) high sensitivity, (2) good anti-interference, (3) high spatial resolution, and (4) fast response speed. Our study may advance new research areas for both the MTJs and pressure sensors.