Nature Phys. 11, 487–491 (2015)

Reconfigurable one- and two-dimensional magnonic crystals — artificial periodic magnetic lattices — have been produced by using patterns of light to induce thermal gradients in magnetic media. Marc Vogel and co-workers from the University of Kaiserslautern and the Fraunhofer Institute for Physical Measurement Techniques in Germany sent spatial intensity patterns of laser light formed by a spatial light modulator into a 5-μm-thick ferromagnetic yttrium–iron–garnet (YIG) waveguide grown on a 500-μm-thick gadolinium–gallium–garnet substrate. To increase the efficiency of the laser-induced heating, a black coating was deposited on top of the YIG. The resulting heat landscape locally changes the saturation magnetization of the YIG and thus alters spin-wave propagation and behaviour. The researchers use the approach to fabricate structured magnonic crystals and suggest that the approach could prove useful for ultrafast spintronic control if femtosecond laser pulses and nanometre-thick magnetic layers are used.