A modal approach to modelling spin wave scattering

Efficient numerical methods are required for the design of optimised devices. In magnonics, the primary computational tool is micromagnetic simulations, which solve the Landau-Lifshitz equation discretised in time and space. However, their computational cost is high, and the complexity of their output hinders insight into the physics of the simulated system, especially in the case of multimode propagating wave-based devices. We propose a finite-element modal method allowing an efficient solution of the scattering problem for dipole-exchange spin waves propagating perpendicularly to the magnetisation direction. The method gives direct access to the scattering matrix of the whole system and its components. We extend the formula for the power carried by a magnetostatic mode in the Damon-Eshbach configuration to the case with exchange, allowing the scattering coefficients to be normalised to represent the fraction of the input power transferred to each output channel. We apply the method to the analysis of spin-wave scattering on a basic functional block of magnonic circuits, consisting of a resonator dynamically coupled to a thin film. The results and the method are validated by comparison with micromagnetic simulations

Electro‐mechanical actuators for general aviation fly‐by‐wire aircraft

A long‐term goal for general aviation aircraft is to reduce or eliminate the use of fluid power systems such as hydraulics from the aircraft. Power‐By‐Wire (PBW) technology seems to be the next major step in the development of aircraft control. In this solution, control power comes directly from the aircraft electrical system to the Electro‐Mechanical Actuator (EMA), which includes the electric motor, controller and gearbox. EMAs have the potential to be more efficient, less complicated, less expensive, and more faults tolerant than actuators based on hydraulic systems. First Published Online: 14 Oct 201

Advanced magnon-optic effects with spin-wave leaky modes

We numerically demonstrate the excitation of leaky spin waves (SWs) guided along a ferromagnetic stripe by an obliquely incident SW beam on the thin film edge placed below the stripe. During propagation, leaky waves emit energy back to the layer in the form of plane waves and several laterally shifted parallel SW beams. This resonance excitation, combined with interference effects of the reflected and re-emitted waves, results in the magnonic Woods anomaly and significant increase of the Goos-Hanchen shift magnitude. Hence, we provide a unique platform to control SW reflection and to transfer SWs from a 2D platform into the 1D guiding mode that can be used to form a transdimensional magnonic router

Theoretical study of the spin wave beams in thin ferromagnetic films

Wydział FizykiFale spinowe są obiecującym nośnikiem informacji, których wykorzystanie może przyczynić się do stworzenia nowej klasy układów do przetwarzania informacji, układów magnonicznych, o wyższej wydajności i mniejszej energochłonności niż układy elektroniczne. Współcześnie najczęściej rozważa się fale spinowe rozchodzące się w postaci fal płaskich. Jednakże, alternatywnym rozwiązaniem jest wykorzystanie wiązek fal spinowych propagujących w jednorodnych układach planarnych. Wiązki te mogą być wykorzystane zarówno, jako nośnik informacji jak i narzędzie eksperymentalne do badania właściwości magnetycznych przy krawędziach cienkich warstw z dużą rozdzielczością przestrzenną. Głównym celem niniejszej pracy doktorskiej było teoretyczne badanie wiązek fal spinowych w cienkich warstwach magnetycznych. Badania były skoncentrowane na koherentnych i monochromatycznych wiązkach, w szczególności analizowane było ich zachowanie w niejednorodnych układach ferromagnetycznych. Zbadane i opisane zostały takie zjawiska jak odbicie i załamanie wiązek fal spinowych oraz efekt Goosa-Hänchen w odbiciu oraz transmisji. Zbadane zostało również uginanie wiązek fal spinowych spowodowane niejednorodnym polem magnetycznym oraz efekt kolimacji fal. Ponadto, w pracy zaproponowana została metoda wzbudzania wiązek fal spinowych przy wykorzystaniu mikrofalowych anten koplanarnych o modulowanej szerokości.Spin waves are promising information carriers and their utilization can result in designing a new class of efficient and low energy consuming information processing devices – magnonic units. Nowadays, the most popular approach is consideration of spin waves propagating in the form of plane-waves or spin waves propagating in confined structures. However, magnonic devices based on planar structures with the spin wave beams can be also exploited to transfer and process information. Moreover, the spin wave beams could be used as a tool to study magnetic properties locally and to deeper knowledge about spin wave dynamics. The main objective of the thesis is the theoretical analysis of spin wave beam dynamics in ferromagnetic films. The research is focused on the coherent low-divergence spin wave beams. Spin wave beams reflection, refraction, lateral shifts along the interface between incident and reflected (or transmitted) beam spots (Goos-Hänchen effect), and beam bending due to non-uniform internal magnetic field are extensively analyzed. Also, the collimation of monochromatic beams of spin waves has been studied. Furthermore, the method suitable for spin wave beams excitation using width-modulated microwave transducers is proposed. The designed microwave antennae enables excitation of multiple spin wave beams of different widths in the single ferromagnetic film

Softening of spin waves in thin magnetic films with perpendicular magnetic anisotropy

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