The progress in manufacturing nanostructured materials has opened new opportunities for exploring the interplay between superconductivity and ferromagnetism in hybrid systems. Hybrid systems offer new ways of designing system functionality by combining materials with different, even antagonistic properties. Through the proximity effect, the close contact between these materials leads to modifications of their properties. Superconductor-normal metal systems have been studied for a long time facilitated by the fact that superconducting correlations can extend into the normal metal over distances of micrometers. Superconductor- ferromagnet systems require a much more precise control over the system parameters as the relevant length scales are in the nanometer range. Technological progress has enabled that level of accuracy only very recently. Since then a number of interesting effects in superconductor-ferromagnet systems caused by the incompatibility of the spin properties of the two materials have been explored. Examples include a non-monotonic dependence of the transition temperature on the thickness of the F layer in S/F bilayers, the possibility of π-Josephson junctions at certain thicknesses of the F layer in S/F/S trilayers as well as the generation of triplet supercurrent in the presence of ferromagnets with non-collinear magnetization.

While most experiments on hybrid systems use resistive measurements, screening of an external magnetic field offers an alternative tool to study the proximity effect. These measurements probe deeply into the superconducting state because they provide both the magnitude and temperature dependence of the effective density of superconducting electrons. Due to the oscillatory behavior of the order parameter in S/F hybrids, screening properties are nontrivial. We studied the screening properties of bi-layer superconductor-ferromagnet films. See M. Houzet and JSM, Magnetic screening properties of superconductor-ferromagnet bilayers, Phys. Rev. B 80, 012505 (2009); arXiv:0903.2245. Experiments are performed in the group of T. Lemberger.

Currently I am mainly interested in dynamic and spin properties of superconductor-ferromagnet hybrid structures.