Optically reconfigurable magnetic materials

The periodic modulation of the magnetic properties of magnonic crystals controls the flow of spin waves. An optical method is now shown that can produce such modulations by heating, which can be reprogrammed during operation. 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 processing1,2,3,4,5, filtering6,7,8 and short-time data storage9. 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.