MgO Magnetic Tunnel Junction Electrical Current Sensor With Integrated Ru Thermal Sensor

Full Wheatstone bridge electrical current sensor incorporating 114 MgO-based magnetic tunnel junction elements (3 × 30 μm²) connected in series was produced for improved electrical robustness. To that end, magnetic tunnel junctions with R × A ~7 KΩ μm² tunneling magnetoresistance of 200%, were produced. The sensor was designed with an integrated Ru thin film resistive thermal detector (RTD) for temperature drift monitoring and compensation. In order to achieve a full bridge signal, a U-shaped copper trace was placed under a printed circuit board (PCB) specifically designed for this type of device. The resulting device exhibit sensitivities of 63.9 V/Oe/A in a 75 Oe linear range biased with 1 mA current, providing a significantly advantageous alternative to AMR and GMR based bridges.