Multifunctional magnetooptical sensors for the measurements of magnetic fields, electrical quantities, and temperature

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Challenges for the applications of magnetic sensors vary greatly. In addition to the regular measurements of magnetic field quantities an important field of application of magnetic sensors is the indirect measurement of electrical quantities, in particular the electrical current. The aim of the project is to investigate multifunctional magnetooptical sensor elements that allow simultaneous optical measurements of additional functional parameters, in particular the measurement of temperatures and electric voltage. This will be achieved using magnetooptically active ferrimagnetic garnet layers. The read-out scheme is based on the temperature dependence of saturation magnetization and thus the corresponding variation of the magnetooptical Faraday effect in connection with characteristic changes in the magnetization response in the layers and of the magnetic domain walls. For the electric voltage measurements, the use of magnetoelectric effects are investigated. All studies are supported by in-operando magnetic domain observations. An essential part of the investigations is devoted to basic research on the various sensor mechanisms and the unraveling of the different signal influences for the simultaneous measurement of the respective quantities. The question of whether optical, local, and simultaneous measurements of quantities like temperature, magnetic field strength, electric current and electrical voltage can be detected with a single multifunctional sensor is at the center of the project. Such a broadband and optical readout sensor could decisively alter measurement methods to ensure the operational safety in electrical systems.