Control of switching time and energy dissipation for ultrafast photo-magnetic recording in dielectrics

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Recently, it was discovered that without any external magnetic field, only by a single laser pulse, selective and reversible photo-magnetic switching in Co-doped yttrium iron garnet films (YIG:Co) can be obtained. This recording was characterized by an extremely short switching time of about 20 ps at room temperature. Moreover, because of its resonant character the write–read events are accompanied by an unprecedentedly low heat load [1]. Microscopically, in this mechanism incident linearly polarized pump pulse excites strongly anisotropic garnet ions, generating an effective field of photo-induced magnetic anisotropy [2],[3].Here, we demonstrate the tunability of both magnetocrystalline and photo-induced anisotropies by the engineering of Co-doped thin iron garnet films and temperature variation. All experimental results were obtained using the time-resolved two-color pump and probe setup at Faraday geometry. The setup was tailored to perform the time-resolved femtosecond single-shot imaging on a CCD camera assuring obtain high temporal and spatial sensitivity.Through modifying the pump light fluence we were able to introduce a change in the light-induced anisotropy field. It allowed us to observe the change of switching times of magnetization and decrease it even more by two times but at the expense of the greater energy required to achieve the switching threshold using a single pump laser pulse. On the other hand, by steering the sample temperatures in the 100-450 K, the range we triggered a change in the magnetocrystalline anisotropy field. Increasing it allowed us to decrease the energy dissipation threshold required for switching over five times. However, decreasing the switching threshold comes at the expense of a longer switching time. Moreover, we demonstrate that the photo-magnetic recording-based garnet medium operates within an extremely large temperature range between -100°C to 100°C. This finding reveals the principles to be employed in achieving cold and ultrafast magnetic recording in dielectrics far beyond today’s state-of-the-art.