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, which covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with the Boolean digital data, unconventional approaches, such as neuromorphic computing, and the progress toward magnon-based quantum computing. This 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.

A novel type of exchange spring media is proposed for magnetic recording systems consisting of a hard/soft bilayer. Finite element micromagnetic simulations show that the reversal modes induced by the external write field are significantly different from the thermally activated switching processes. Thus, the bilayers can be optimized in order to achieve a high thermal stability without increase of coercive field. In grains with identical size and coercivity an optimized bilayer reaches an energy barrier exceeding those of optimized single phase media by more than a factor of two. Additionally the lower angular dependence of coercivity of exchange spring media will improve the signal to noise ratio.

The concept of exchange spring media is extended from two layers to $N$ layers. The coercive field of the multilayer structure decreases with $1∕N$ while the energy barrier is only determined by the magnetic properties of the hardest layer. A $25\mathrm{nm}$ thick trilayer has a 7.5 times smaller coercive field $\left(1.4\mathrm{T}\right)$ as a single layer at the same thermal stability and for the same value of the magnetization. A continuous variation of the anisotropy in the recording media reduces the coercive field by a factor of 10 for a layer thickness of $25\mathrm{nm}$ .