The interaction of Magnetism and Superconductivity in Thin Films Probed by Low Energy Muon Spin Rotation
Dr Stephen Lee
Thin films and multilayers provide an interesting means to study the interaction of the normally antagonistic order parameters associated with ferromagnetism (F) and superconductivity (S). Some interesting states can indeed be most easily realised in thin film architectures. The existence of Larkin–Ovchinnikov-Fulde–Ferrell (LOFF) states, for example, has been most convincingly demonstrated in thin film superconducting-ferromagnetic (SF) hybrid devices. The formation of odd-frequency spin-triplet states in S/F structures is another example where thin film geometries lead to a new physical state.
Resolving local and depth-dependent information on such structures is experimentally challenging, especially when connected with buried interfaces. Low energy muon-spin rotation (LE-µSR) is a powerful probe of thin film magnetic structures, giving high sensitivity to local magnetic fields while possessing some level of depth resolution.
I will discuss a number of recent experiments on superconducting-ferromagnetic systems probes using LE-µSR. Examples will include unusual magnetic states in S/F, S/N(normal) and S/F/N hybrids, including the observation of time-reversed paramagnetic Meissner states, unusual aspects of conventional Meissner effects and some novel diamagnetic Meissner states in the presence of F layers.