Science 345, 1337–1340 (2014)

Controlling the behaviour of magnetic systems without resorting to the use of applied magnetic fields offers tantalizing prospects for data memory and storage technologies. Optical manipulation is one way to achieve low-power, rapid control of the magnetization, but the catch is that up until very recently, this was only possible with a limited selection of materials containing rare-earth elements and characterized by antiferromagnetic exchange interactions.

Charles-Henri Lambert and colleagues have now generalized this concept to thin ferromagnetic structures. In one fell swoop, the authors dramatically expanded the range of possible systems suitable for optomagnetic switching, and showed that antiferromagnetic interactions are not a key ingredient for this phenomenon, as previously thought.

The optical switching depends on the helicity of the circularly polarized laser beam impinging on the magnet, and is demonstrated on ferromagnetic systems such as Co films, as well as Co/Pt and Co/Ni multilayers, provided they are thin enough. This is thought to be a consequence of the small demagnetization energy due to dipolar interactions, which would otherwise be overwhelming in the bulk limit. Optical control of ferromagnetic bits may be feasible after all.