Structuring of materials is the most general approach for controlling waves in solids. As spin waves - eigen-excitations of the electrons' spin system - are free from Joule heating, they are of interest for a range of applications, such as processing, filtering and short-time data storage. Whereas all these applications rely on predefined constant structures, a dynamic variation of the structures would provide additional, novel applications. Here, we present an approach for producing fully tunable, two-dimensionally structured magnetic materials. Using a laser, we create thermal landscapes in a magnetic medium that result in modulations of the saturation magnetization and in the control of spin-wave characteristics. This method is demonstrated by the realization of fully reconfigurable one- and two-dimensional magnonic crystals - artificial periodic magnetic lattices.
