Reine Spinströme in lateralen Spinventilen:in situ\textit{situ} Erzeugung und Nachweis

The subject of this thesis at hand is the generation of pure spin currents in lateral spinvalves.Pure spin currents result from the accumulation of spins and give rise to spin transport in theabsence of charge transport. The diffusive character of spin transport may be the key to prospectiveconcepts for information transmission and processing with significantly reduced dissipation.The investigation of pure spin currents also contributes to a deeper understanding of spin-basedphenomena such as magnetoresistance (e.g. GMR, TMR) and magnetization dynamics (e.g. spintransfertorque STT) by addressing fundamental spin transport and relaxation processes.In order to create a pure spin current, a charge current is injected into a ferromagnet/ nonmagnetinterface. The multi-terminal geometry for local and non-local electrical transport measurementsand the size of the diffusion channel needed for the generation and detection of pure spin currentsrequire a sequence of laterally connected ferromagnetic and nonmagnetic leads on thesubmicron scale, the so called lateral spinvalve. Besides local and non-local electrical transportmeasurements, imaging of the ferromagnetic parts and the diffusion channel by scanning electronmicroscopy with polarization analysis (SEMPA) is employed as an analysis tool. The intent ofapplying SEMPA to the nonmagnetic diffusion channel is to directly image the spin accumulation,which would provide new knowledge about the dynamics, propagation, and relaxation of spincurrents. The small information depth of SEMPA and the crucial importance of clean interfacesand surfaces for the creation of pure spin currents are the motivation to realize the entire samplefabrication and investigation in situ in a complex ultra-high vacuum system.A novel multi-stage fabrication process based on thermal evaporation and structuring with anfocused ion beam system (UHV-FIB) is developed. Thereby, the design of a sample layout givingrise to a single-domain magnetization patterns in the two ferromagnetic leads and allowing forhigh-resolution SEMPA imaging even during the current-induced generation of a pure spin currentturned out to be the major challenge. The development steps to achieving these goals and thederived experience and know-how are presented in detail. An important aspect for interpretingthe non-local transport signal in a spinvalve is the distinct understanding of the remagnetizationprocesses in the nanoscale magnets. This is achieved by a combined analysis of 2-pointmeasurements of the anisotropic magnetoresistance (AMR) effect and SEMPA images of the ferromagnets.For Co/Cu spinvalves the successful detection of pure spin currents is evidenced bycorrelating non-local electrical transport measurements to AMR and SEMPA data. The observedeffect size is in agreement with published work of other groups and indicates the high qualityof the ferromagnet/nonmagnet interfaces in our spinvalves. Imaging of the spin accumulation inthe nonmagnet by SEMPA did not show not the assumed results. Likely reasons as well as otheropen questions are finally discussed