Evaluation of the Feasibility of TMR Sensor Array Vertical Packing for Enhanced Detectivity
Filipe Favita, Pedro D. R. Araujo, Francisco Matos, Susana Cardoso, P. P. Freitas · IEEE Transactions on Magnetics · 2025
Increasing the number of vertically packed magnetic sensors in parallel has been proposed to improve field detectivity. However, practical implementation of these ultracompact architectures suffers from the increased surface roughness and magnetic coupling between tunneling magnetoresistance (TMR) levels, which can negatively impact the sensor’s performance. To mitigate these effects, several strategies are evaluated in this work: aligned, shifted, and alternating integration of the TMR arrays. Moreover, different free layer sensitivities are explored, using NiFe and CoFeBSi free layers. Among these, the optimized geometry is shown to be two-level TMR sensors distributed in an alternating geometry that demonstrated superior performance to single-level TMR arrays, achieving a detectivity of 3.9 nT$\cdot $Hz${}^{-1/2}$with a NiFe free layer and 8.3 nT$\cdot $Hz${}^{-1/2}$at 10 Hz with a CoFeBSi-based free layer.