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Institute for Measurement Technology
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Bachelor Theses.

Analyzation and optimization of a Faraday Rotation Magnetometer in order to measure magnetic microstructures

Thomas Krainer

A Faraday Rotation Magnetometer is used to measure magnetic microstructures. It utilizes the Faraday effect to measure magnetic fields. In order to achieve this, a light source in combination with a polarizing filter is used to generate linear polarized light. The polarization state is changed when the light passes through a sensor while a magnetic field is present. The rotation of the light is proportional to the strength and direction of the magnetic field. Another polarizing filter is used to translate the change of polarization into a change of intensity. After that the generated picture is captured by a digital camera.

Fig. 1: Composition of the extended Faraday Rotation Magnetometer Fig. 1: Composition of the extended Faraday Rotation Magnetometer

For this thesis the used Faraday Rotation Magnetometer was optimized with regard of its components. In order to improve the sensor illumination a stronger LED in combination with an optical filter was used. This led to an overall increase in brightness and homogeneity. Further on, two crystals were analyzed. It was determined that each of them must be used in a different measuring range. In addition to that, an optical magnification was added. By using a different camera, the picture noise was reduced. Finally, the two polarizing filters were examined. It was possible to determined, that these are best used while being rotated 45 degrees relative to each other. This yields the greatest change in intensity in relation to a change in polarization.

Keywords: Faraday Rotation Magnetometer, Faraday effect, Helmholtz coil, magnetic field measurement

August 25, 2021