Optimisation of Spin-Valve Planar Hall Effect Sensors for Low Field Measurements

Abstract

In this paper are presented results of galvanomagnetic measurements and micromagnetic simulations performed on low-field magnetic sensors based on the planar Hall effect (PHE). Disc-shaped structures of the type Co/Cu/Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">80</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> , 4 mm diameter, deposited by magnetron sputtering onto Si substrate, were used to build magnetic sensors. At this stage of study, no uniaxial anisotropy axes were defined during the samples deposition. Two types of applications have been considered: (i) magnetic field measurements and (ii) rotation sensing. In order to obtain a coherent rotation of the magnetization inside the PHE sensor under the action of an applied magnetic field, H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">appl</sub> , DC or AC magnetic biasing fields were used. By these means the magnetic sensitivity and the hysteresis width of the PHE signal can be tuned. Sensitivities between 0.07 and 0.17 μV·A <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ·m have been obtained for a driving current of 10 mA. Micromagnetic simulations were used to explain some field angular behavior of these sensors.