All-Optical Helicity-Dependent Switching in Hybrid Metal–Ferromagnet Thin Films

摘要

Over the past decades, optical manipulation of magnetization by ultrafast laser pulses has attracted extensive interest. It not only shows intriguing fundamental science arising from the interactions between spins, electrons, phonons, and photons, but also manifests the potential to process and store data at a speed that is three orders of magnitude faster than the current technologies. In this paper, all-optical helicity-dependent switching (AO-HDS) in hybrid metal-ferromagnet thin films, which consist of Co/Pt multilayers with perpendicular magnetic anisotropy and an Au film capping layer on the top, is experimentally demonstrated. The switching behaviors of the hybrid Co/Pt-Au material, with various laser repetition rates, scanning speeds, and fluencies, are systematically studied. In comparison with bare Co/Pt multilayers, the hybrid metal-ferromagnet thin films show pronounced AO-HDS when the number of laser pulses per mu m along the scanning direction gradually increases. In addition, the AO-HDS effect is very robust against laser fluences. A possible mechanism is further proposed based on numerical simulations of the optomagnetic coupling model. These findings promise a new material system that exhibits stable AO-HDS phenomena, and hence can transform future magnetic storage devices, especially with the addition of plasmonic nanostructures made of noble metals.