Substantial and stable magnetoresistance and spin conductance in phosphorene-based spintronic devices with Co electrodes.

Designing devices with excellent spin-polarized properties has been a challenge in physics and materials science. In this work, we report a theoretical investigation of the spin injection and spin-polarized transport properties of monolayer and bilayer phosphorene devices with Co electrodes. Based on the analysis of transmission coefficients, spin-polarized current, magnetoresistance (MR) (or tunnel MR) ratio and spin injection efficiency (SIE), both devices show superior spin-polarized transport properties. As phosphorene in the device is changed from monolayer to bilayer, the charge carrier type can be tuned from n-type to p-type. For the monolayer phosphorene device, the tunnel MR ratio reaches about 210% and the SIE is about 80.7% at zero bias. Notably, the SIE and tunnel MR ratio maintain almost constant values against bias voltage and gate voltage, which makes it suitable for magnetic sensors. As for the bilayer phosphorene device, it not only exhibits a considerable tunnel MR ratio, but also shows significantly enhanced conductance, beneficial to the sensitivity of spintronic devices. Further analysis shows that the improvement of conductance is attributed to the low barrier height between the bilayer phosphorene channel and Co electrodes. According to our results, the studied phosphorene devices with Co electrodes demonstrate superior spin injection and transport properties. We believe that these theoretical findings will be a strong asset for future experimental works in spintronics.