Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of current challenges and the outlook of further development for each research direction.

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A special design of an oxide-based transversal thermoelectric device utilizing thermoelectric oxides in combination with a ceramic multilayer technology is proposed. Metal strips within the ceramic matrix replace the tilted stack of alternating layers used in artificial anisotropic transversal thermoelectric devices. Numerical three-dimensional simulations of both device types reveal better thermoelectric performance data for the device with metal stripes. A monolithic transversal strip-device based on the material combination La1.97Sr0.03CuO4/Ag6Pd1 was prepared and electrically characterized. A maximum power output of 4.0 mW was determined at ΔT = 225 K for the monolithic device. The observed results are in remarkable agreement with three-dimensional numerical simulations utilizing the transport parameters of the two materials and the geometry data of the device.

Oxide multilayer thermoelectric generators (MLTEG) were fabricated, using the standard multilayer technology. Green tapes of p-type La2CuO4 and n-type Nd2CuO4 thermoelectric oxides were stacked with intermediate insulating glass layers. Electrical contacts between thermoelectric oxides were applied, using screen-printing of AgPd paste, and multilayers were cofired at 1000°C. However, cofiring of four different materials turned out to be very challenging, and contact resistance problems frequently led to device malfunctions. We developed a new concept of a transversal multilayer thermoelectric generator (TMLTEG), which is characterized by a simple design. This generator is build up by stacking layers of a p- or n-type thermoelectric oxide and printing stripes of AgPd paste onto the thermoelectric layers at an angle with respect to the temperature gradient. Transversal multilayer thermoelectric generators were fabricated using p-type La2CuO4, or n-type substituted CaMnO3; cofiring of the multilayer stacks was performed at 1000°C. The TMLTEG based upon p-type lanthanum cuprate exhibits a power output of 7.8 mW at ∆T= 200 K in the low temperature range of 25-135°C. Materials issues, cofiring characteristics, design and the thermoelectric performance of multilayer TEGs will be discussed