Nano Lett. http://doi.org/ck73 (2018)

All-optical switching of a material between antiferromagnetic and ferromagnetic behaviour is important for information processing and recording technology. Now, by investigating a wide range of multisublattice magnetic materials, John Dewhurst and co-workers from Germany have unveiled the microscopic mechanism for the switching. A laser pulse with a duration of 25 fs and an energy fluence of 16 mJ cm–2 was sent to a multilayer material system consisting of two monolayers of Mn and four monolayers of Co. The time evolution of the ground-state magnetic moment of each layer and the flow of optically induced spin-selective charge were measured. Following exposure to the optical pulse, the magnetic moment of one of the Mn monolayers changed and the multilayer consequently became demagnetized at a time of 29 fs after pulse irradiation. The German scientists further investigated Fe/Mn multilayers using a laser pulse of duration of 12.5 fs and found that the demagnetization occurred around 12–15 fs. These results seem to demonstrate that optically induced charge flow is the key to controlling spin dynamics.