This paper presents an initial approach to investigate the feasibility of fabricating FSF heterostructures, for potential applications in spintronics. These FSF stacks could help characterize long...Show moreThis paper presents an initial approach to investigate the feasibility of fabricating FSF heterostructures, for potential applications in spintronics. These FSF stacks could help characterize long-range triplet Cooper pairs that are created at its interfaces. Simulations inform the final design of a 3D FSF stack, composed of one low and one high aspect ratio rectangular shape. Subsequent efforts were directed on the focused ion beam milling of apertures in 1 µm thick Si3N4 membranes that are used for shadow evaporation of the heterostructures. Several stacks of cobalt and niobium were fabricated with these membranes through shadow evaporation. These heterostructures were contacted via electron beam lithography and measured in a vectormagnet cryostat. Results indicate that no long-range triplets were generated inside the FSF stacks. It can be concluded that either the niobium layers did not become superconducting or the magnetization of the two ferromagnets in the stacks were not perpendicular.Show less
In the vicinity of the superconducting dome in the phase diagram of iron-pnictides there exist a magnetically ordered phase accompanied by a nematic phase and a structural transition. Since all...Show moreIn the vicinity of the superconducting dome in the phase diagram of iron-pnictides there exist a magnetically ordered phase accompanied by a nematic phase and a structural transition. Since all three phases belong to the same point group symmetry, it is a priori difficult to establish which of these phases is dominant. The fluctuations associated with the energetically dominant transition have been proposed as the driving force behind electronic pairing in the superconducting state. Therefore the identification of this transition is essential for further understanding the physics behind superconductivity in iron-pnictides. This thesis explores the relation between nematic strength and the superconducting critical temperatures in the pnictides. The in-plane resistivity anisotropy of single crystal SmFeAsO (Tc =55 K in optimally F-doped SmFeAs[O,F]) was investigated using four different sample geometries structured by focused ion beam methods. The results are compared to other iron-pnictides and it was observed that the maximal resistivity anisotropy is similar as to that in other iron-pnictides. These initial results clearly lay the groundwork for future experimental studies, in particular probing the relation between the crystal lattice and the nematicity.Show less
