Ultrasensitive Nanoscale Magnetic-Field Sensors Based on Resonant Spin Filtering

We propose magnetic-field sensors based on the magnetoresistance (MR) physics of resonant spin filtering and present device designs catered toward exceptional magneticfield sensing capabilities. Using the nonequilibrium Green's function spin transport formalism self-consistently coupled to the Poisson's equation, we present highly tunable pentalayer magnetic tunnel junction (MTJ) structures that are capable of exhibiting an ultrahigh peak tunnel MR (≈2500%). We show how this translates to device designs featuring an ultrahigh current sensitivity enhancement of over 300% in comparison with typical trilayer MTJ sensors, and a wider tunable range of field sensitivity. We also demonstrate that a dynamic variation in sensor functionalities with the structural landscape enables a superior design flexibility over typical trilayer sensors. An optimal design exhibiting close to a 700% sensitivity increase as a result of angle-dependent spin filtering is presented. In exploring the robustness of device designs, we find that the spin-filtering scheme, and hence, the associated designs are reasonably immune to elastic dephasing. This paper sets a stage to engineer spintronic building blocks via the design of functional structures tailored to exhibit ultrasensitive spin filtering.