Low Hysteresis and High Stability in Tunneling Magnetoresistance Vortex Sensors With a Composite Free Layer

The linearity of tunneling magnetoresistance (TMR) sensors is challenging due to the intrinsic magnetic hysteresis of the ferromagnetic Co-Fe-B layer used as the free layer. In this work, by using a composite free layer of Co-Fe-B/Ta/Co-Fe-Si-B with optimized geometric, we demonstrate vortex magnetic states in TMR sensors with large magnetic tunneling junctions, leading to low hysteresis and high stability under external magnetic fields, with a sensitivity of 6 mV/V/Oe (0.6% Oe
$^{-{1}}$
) and a nonlinearity below 0.5% FS within ±20 Oe. TMR vortex sensors with a composite free layer could be potentially useful in high precision current sensing in harsh environment.