Multi-pulse induced successive magnetization switching of GdFeCo alloys

The photon energy injected into free electrons of ferrimagnetic alloys via linearly polarized light induces magnetic system non-equilibrium, triggering all-optical magnetization switching. Write-erase events under the excitation of two consecutive laser pulses have been extensively studied. However, high-speed data processing depends more largely on the repetition rate of magnetization switching under the excitation of multiple consecutive laser pulses. To this end, the variation of magnetic moments in ferrimagnetic alloys under the excitation of multiple consecutive laser pulses is investigated based on a semiclassical atomic spin dynamics model. Although the non-equilibrium electron state allows rapid double switching, cumulative lattice heating from multiple pulses necessitates longer cooling times for subsequent switches to avoid thermal saturation of the magnetic system. It is shown that stable continuous magnetization switching requires a pulse separation of more than 100 ps. However, reducing the system's demand for excitation laser energy by the pre-laser and reducing the energy density threshold of subsequent lasers is expected to break the limitation of repetition rate by substrate cooling in a phased manner.