Manipulating spin waves in ferromagnetic microstructures

Over the past decades computing devices decreased drastically in size. When an electric charge is used for the information transfer a number of problems can arise, which prevent an effective work of such logic devices. For that reason, new ways of information processing are actively researched. One of promising candidates are spin waves or magnons. They allow to transfer information using purely magnetic properties of the materials. The latter gives an opportunity to transfer bigger amounts of information much faster then with an electrical charge. However, before moving to real application thorough fundamental research is of utmost importance. A wide range of geometrical systems of various materials suitable for transferring spin waves has been investigated at this point, including nanometer range thin films, multilayer nanostructures, magnonic crystals, magnonic waveguides and confined microstructures. In this project the focus is put on a fundamental understanding of the dynamic magnetic properties of confined structures, as this is a prerequisite for the development of nanoscale computational devices based on magnetism. In the previous research of the principal investigator it was shown that devices geometry variation can possibly be used in order to manipulate spin waves. This principle is planned to be exploited in the project. The influence of the devices shape will be systematically investigated using experimental and theoretical approach in order to be able to controllably excite and manipulate spin waves in confined structures using simple excitation scheme.

To prevent the energy crisis of the near future, one needs to search for new approaches in technology development already now. One of the biggest contributions to that nowadays is computing. Modern computational technologies, such as artificial intelligence (AI), have provided enhanced features for modern devices and data processing, but as well the total energy consumption by general-purpose computing continues to grow exponentially and is doubling approximately every 3 years while the world's energy production is growing only linearly, by approximately 2% a year. One can approach this problem, e.g. optimizing computing strategies, as is already actively researched for AI, so-called AI research strategies. Another way would be making computing devices more energy efficient. Magnonics is a promising research field in this regard, as it employs spin waves (magnons), purely magnetic waves, for information transport and processing. Among other advantageous features, magnonic devices can be scaled down to atomic dimensions, can operate in a wide frequency range up to hundreds of terraherz, are able to process data at temperatures spanning from ultra-low to room temperature. Additionally, spin waves can transfer data without Joule heating and can make unconventional computing possible due to their nonlinear properties. Moreover, there has been increasing interest in studying spin waves, in various geometries, including curved structures, as 3D curvature can introduce unique magnetic properties and novel phenomena due to the interplay of curvature, topology, and magnetic interactions. It is possible to control spin waves by just changing a shape of a wire, in which they are excited, as it was researched and shown in ESP 4 project. Spin waves were researched using micromagnetic simulations, lab- and synchrotron-based measurements. It was shown that, for example, placing two microwires next to each other one can influence movement of a spin wave. Different shape of wires were researched and results were presented in form of science-communication project titled "Spin-Wave Voices" at the annual international digital art exhibition Ars Electronica Festival in 2022 (https://ars.electronica.art/planetb/en/spin-wave-voices/) and at the Exhibition Data Doom Desire in 2024 (https://ail.angewandte.at/explore/exhibition-view:-data-doom-desire/). Additionally, spin-wave behaviour changes over the time from the moment of its excitation untill the stable state is formed was researched. This process nanoseconds and reveals how spin waves can be used for ultrafast devices.