Regensburg 2019 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 32: Magnetic recording, sensors and other devices
MA 32.1: Vortrag
Mittwoch, 3. April 2019, 12:00–12:15, H53
Properties of Magnetoresistive Sensors in Vortex-Configuration — •Christoph Durner1,2, Wolfgang Raberg1, Klemens Pruegl1, and Jonathan Finley2 — 1Infineon Technologies AG, 85579 Neubiberg, Germany — 2Walter Schottky Institute, E24, Technical University of Munich, 85748 Garching, Germany
Many automotive applications, such as wheel speed, require magnetic sensors with negligible small hysteresis and a wide linear operating range. All these requirements can be met using a Tunneling Magnetoresistance (TMR) spin-valve sensor with the free layer (FL) in the vortex (V) state. The V state is characterized by a closed rotationally symmetric magnetization with a centered z-component, the V core. Usually, the FL exhibits a disk-like shape to enable a V-like magnetization. In reality the FL cannot be processed perfectly cylindrical. The shape alteration leads to a variation of the V behavior upon external magnetic fields and therefore, in a modified electrical signal. Micromagnetic simulation were used to successfully match the magnetization of the FL to the observed electric behavior under the influence of an external magnetic field in dependence of differences in FL structuring. Another focus of the investigations was the improvement of the TMR stack, in particular the layers responsible for the tunneling process, namely free layer, tunnel barrier, and reference layer (RL) system. By optimizing the ferromagnetic material composition and thicknesses of the FL and RL significant improvement of the TMR ratio by a factor of two as well as an improved stability of the entire system with respect to high temperature annealing was achieved.