Magnetic Sensors

Magnetic hysteresis of (a) elliptical sensor element subject to shape anisotropy compared to (b) vortex sensor.

Magnetic sensors are used in a wide range of applications, where robust, contactless sensing is required. For example modern cars contain several magnetic sensors to measure wheel speed, transmission gear speed and position, crankshaft position, engine speed, and much more. Currently a transition from the classical Hall effect sensors to GMR (Giant MagnetoResistance) and TMR (Tunnel MagnetoResistance) sensors takes place. Compared with classical sensors, magnetoresistive sensors offer enhanced sensitivity and thus extended range and applicability. 

Due to non-linear and hysteretic effects like domain wall motion or switching events, the device modeling gets challenging. 

Furtunately the underlying physical processes can be well described by micromagnetic simulations. Sensor dimention in the micrometer regime require very efficient numerical methods.

Typical questions which are studied include the effects of bias fields, surface roughness, sensor layout on the overall performance of the sensor. The final goal in sensor design is to reduce non-linearity, hysteresis as well as the magnetic noise of the sensor. One very recent example for an improved sensor design is a low-noise sensor based on topologically protected vortex structures. Utilizing the stable vortex groundstate allows to significantly reduce hysteresis, while providing an extended linear range.

Selected Publications