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PhD Defence Pim Reith

squids, fits and other magnetic bits

Pim Reith is a PhD student in the research group Interfaces and Correlated Electrons. His supervisors are prof.dr.ir. J.W.M. Hilgenkamp and prof.dr.ir. W.G. van der Wiel from the Faculty of Science and Technology.

Magnetism is a property of matter that has been known for thousands of years, yet we have only just begun to understand it. These days, magnets can be found in many everyday applications such as MRI scanners, hard disks and the classic fridge magnet. These days, science and society are focused on energy-efficient and environmental friendly products, meaning material scientists have their work cut out for them.

For the research in this thesis, we used a scanning SQUID microscope. This is a microscope built around a SQUID device, a piece of superconducting circuitry that results in the most sensitive magnetometer we have available. By scanning such a SQUID device across a surface, we can detect and image the magnetic field that object produces. This way, we can learn more about the material: how strong of a magnet it is, if it is magnetic everywhere or not, etc. Even more, we can do this with a resolution of less than 10 micrometres.

This thesis describes a variety of projects that involve scanning SQUID measurements. We have performed experiments on varying material systems, including complex-oxide thin films, ferromagnetic micro- and nanoparticles and superconducting microstructures. We not only attempted to learn more about these systems this way, but also to improve the analytical methods to increase the value of the data obtained with the system.