Reflection and Refraction of Spin Waves

In this thesis, wave effects associated with the refraction and reflection of plane, dipolar spin waves are investigated. All measurements are conducted with time-resolved scanning Kerr microscopy. This magneto-optical technique allows for imaging of phase-resolved magnetization dynamics in real space, thereby providing a direct access to wave characteristics: By fitting their interference pattern, wave vector, phase, and attenuation length can be quantified. The anisotropic dispersion relation in the dipolar regime depends on the thickness of a ferromagnetic film. Therefore, a thickness step acts as a boundary between two media of different indices of refraction. In two related experiments, the refraction and reflection of spin waves at the interface between a thick Ni80Fe20 (Py) film and a thin Py film are investigated and Snell's law for spin waves is proven. In addition, the reflection of spin waves from an edge of a Py film is studied. There, the plane wave exhibits a phase shift reminiscent of the Goos-Hänchen shift. All experiments provide valuable insight into the refraction and reflection of spin waves. Especially the study of refraction is interesting in the context of magnonics, where concepts to efficiently reduce wavelengths and steer spin waves are actively searched for. Besides these technological aspects, Snell's law and the Goos-Hänchen shift are fundamental wave effects which appear in various contexts throughout physics

Pleiotropic effects in Eya3 knockout mice

<p>Abstract</p> <p>Background</p> <p>In <it>Drosophila</it>, mutations in the gene <it>eyes absent </it>(<it>eya</it>) lead to severe defects in eye development. The functions of its mammalian orthologs <it>Eya1-4 </it>are only partially understood and no mouse model exists for <it>Eya3</it>. Therefore, we characterized the phenotype of a new <it>Eya3 </it>knockout mouse mutant.</p> <p>Results</p> <p>Expression analysis of <it>Eya3 </it>by <it>in-situ </it>hybridizations and β-Gal-staining of <it>Eya3 </it>mutant mice revealed abundant expression of the gene throughout development, e.g. in brain, eyes, heart, somites and limbs suggesting pleiotropic effects of the mutated gene. A similar complex expression pattern was observed also in zebrafish embryos.</p> <p>The phenotype of young adult <it>Eya3 </it>mouse mutants was systematically analyzed within the German Mouse Clinic. There was no obvious defect in the eyes, ears and kidneys of <it>Eya3 </it>mutant mice. Homozygous mutants displayed decreased bone mineral content and shorter body length. In the lung, the tidal volume at rest was decreased, and electrocardiography showed increased JT- and PQ intervals as well as decreased QRS amplitude. Behavioral analysis of the mutants demonstrated a mild increase in exploratory behavior, but decreased locomotor activity and reduced muscle strength. Analysis of differential gene expression revealed 110 regulated genes in heart and brain. Using real-time PCR, we confirmed <it>Nup155 </it>being down regulated in both organs.</p> <p>Conclusion</p> <p>The loss of <it>Eya3 </it>in the mouse has no apparent effect on eye development. The wide-spread expression of <it>Eya3 </it>in mouse and zebrafish embryos is in contrast to the restricted expression pattern in <it>Xenopus </it>embryos. The loss of <it>Eya3 </it>in mice leads to a broad spectrum of minor physiological changes. Among them, the mutant mice move less than the wild-type mice and, together with the effects on respiratory, muscle and heart function, the mutation might lead to more severe effects when the mice become older. Therefore, future investigations of <it>Eya3 </it>function should focus on aging mice.</p

Dynamic detection of current-induced spin-orbit magnetic fields

Current-induced spin-orbit torques (SOTs) in ferromagnet/nonmagnetic metal heterostructures open vast possibilities to design spintronic devices to store, process, and transmit information in a simple architecture. It is a central task to search for efficient SOT devices, and to quantify the magnitude as well as the symmetry of current-induced spin-orbit magnetic fields (SOFs). Here, we report an approach to determine the SOFs based on magnetization dynamics by means of time-resolved magneto-optic Kerr microscopy. A microwave current in a narrow Fe/GaAs (001) stripe generates an Oersted field as well as SOFs due to the reduced symmetry at the Fe/GaAs interface, and excites standing spin wave (SSW) modes because of the lateral confinement. Due to their different symmetries, the SOFs and the Oersted field generate distinctly different mode patterns. Thus, it is possible to determine the magnitude of the SOFs from an analysis of the shape of the SSW patterns. Specifically, this method, which is conceptually different from previous approaches based on line shape analysis, is phase independent and self-calibrated. It can be used to measure the current-induced SOFs in other material systems, e.g., ferromagnetic metal/nonmagnetic metal heterostructures

Spin-wave wavelength down-conversion at thickness steps

We report a systematic experimental study on the refraction and reflection of magnetostatic spin-waves at a thickness step between two Permalloy films of different thickness. The transmitted spin-waves for the transition from a thick film to a thin film have a higher wave vector compared to the incoming waves. Consequently, such systems may find use as passive wavelength transformers in magnonic networks. We investigate the spin-wave transmission behavior by studying the influence of the external magnetic field, incident angle, and thickness ratio of the films using time-resolved scanning Kerr microscopy and micro-focused Brillouin light scattering. (C) 2018 The Japan Society of Applied Physic