Light-wave dynamic control of magnetism.

The enigmatic interplay between electronic and magnetic phenomena observed in many early experiments and outlined in Maxwell's equations propelled the development of modern electromagnetism. Today, the fully controlled evolution of the electric field of ultrashort laser pulses enables the direct and ultrafast tuning of the electronic properties of matter, which is the cornerstone of light-wave electronics. By contrast, owing to the lack of first-order interaction between light and spin, the magnetic properties of matter can only be affected indirectly and on much longer timescales, through a sequence of optical excitations and subsequent rearrangement of the spin structure.