Magnetic sensor element, sensing device and sensing operation using the sensing device for sensing an external magnetic field with low-noise

A sensing operation using a sensing device comprising:

• at least one sensing branch comprising at least one magnetic sensor element, comprising:
• at least one MTJ comprising, in this order, a reference layer, a tunnel barrier layer, a sense layer, and a capping electrode layer;
• wherein the sense layer has a sense magnetization that is freely orientable in the presence of the external magnetic field in the plane of the sense layer;
• wherein the reference layer comprises a reference SAF structure including a first reference sublayer, having a first reference magnetization, a second reference sublayer having a second reference magnetization and separated from the first reference sublayer by a coupling layer antiferromagnetically coupling the first and second reference sublayers;
• wherein the reference layer has a sensitivity axis in the plane of the reference layer, such that the first and second reference magnetizations are switchable along the sensitivity axis between a first switching direction and a second switching direction opposed to the first switching direction;
• and
• wherein the magnetic sensor element further comprises a SOT electrode, in direct contact with the first reference sublayer and configured to pass a SOT current adapted to switch the first reference magnetization by a spin orbit torque (SOT) interaction in the first or second switching direction, depending on the polarization of the SOT current;
• wherein the sensing device further comprises a controller comprising a SOT line driver configured to control the passing of the SOT current in the SOT electrode of each of said at least one sensing branch;
• and
• a reading circuit configured to control the passing of a read current through the MTJ of each of said at least one sensing branch;
• wherein the sensing operation comprises the steps of:
• controlling the SOT line driver to perform at least one switching cycle comprising passing the SOT current in the SOT electrode with a first direction to switch the first reference magnetization in a first switching direction and passing the SOT current in the SOT electrode with a second direction to switch the first reference magnetization in a second switching direction opposed to the first switching direction;
• for each switching cycle, controlling the reading circuit to pass a read current through the MTJ when the first reference magnetization is in the first switching direction and measure a first resistance of the MTJ, and to pass a read current through the MTJ when the first reference magnetization is in the second switching direction and measure a second resistance of the MTJ;
• and
• for each switching cycle, determining a differential resistance from the difference between the first and second resistances.