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Thermally induced magnetization switching (TIMS) relying solely on a single laser without any applied magnetic field is a key research direction of current spintronics. Most studies on TIMS so far have focused on GdFeCo with Gd concentration above 20%. In this work, we observe the TIMS at low Gd concentration excited by picosecond laser through atomic spin simulations. The results show that the maximum pulse duration for switching can be increased by an appropriate pulse fluence at the intrinsic damping in low Gd concentrations. At the appropriate pulse fluence, TIMS with pulse duration longer than one picosecond is possible for Gd concentration of only 12%. Our simulation results provide new insights for the exploration of the physical mechanism of ultrafast TIMS.

Anderson localization has been observed in various types of waves, such as matter waves, optical waves and acoustic waves. Here we reveal that the effect of Anderson localization can be also induced in metallic nonlinear nanoparticle arrays excited by a random electrically driving field. We find that the dipole-induced nonlinearity results in ballistic expansion of dipole intensity during evolution; while the randomness of the external driving field can suppress such an expansion. Increasing the strength of randomness above the threshold value, a localized pattern of dipole intensity can be generated in the metallic nanoparticle arrays. By means of statistics, the mean intensity distribution of the dipoles reveals the formation of Anderson localization. We further show that the generated Anderson localization is highly confined, with its size down to the scale of incident wavelength. The reported results might facilitate the manipulations of electromagnetic fields in the scale of wavelength., 8 pages, 7 figures, published on Optics Express,24,13210