Magnetization manipulation using ultra-short laser pulses in ferromagnetic cells for spintronics applications

Magnetization reversal processes and magnetization dynamics in general are of utmost importance for many spintronics applications. Such ultrafast dynamics can be measured, e.g., using pump–probe experiments with pulsed lasers, in which a strong pump laser excites a sudden change in the magnetization vector, leading to a precession (measured by the weak probe laser) until the relaxed state is reached again. Such measurements, however, are challenging due to the necessary overlap of both laser beams on the sample. An easier approach would be modeling this process. Such a model has been developed based on the micromagnetic simulation MagPar. Using simulated ultra-short laser pulses, we investigated a matrix of separate ferromagnetic cylindrical cells to prototype possible memory applications. The cells made of FePt were immersed in an MgO layer to satisfy adequate thermal conditions. The heat-transport problem was solved using the two-temperature model. Simulations were performed using the micromagnetic Landau–Lifshitz–Bloch (LLB) equation and the finite element method (FEM) to mimic realistic shapes of material objects as well as to include magneto-optic and thermal fields. The calculations were carried out for different distances between cells and a variety of laser pulse durations and intensities. The obtained results provide information about stability conditions for magnetization states and the possible spatial density of such memory devices.