Co/Pt multilayers with perpendicular magnetic anisotropy are irradiated by focused He⁺ ion beam to locally reduce the anisotropy value. The irradiated spots with a diameter of 100 nm are arranged in a square lattice with 200 nm period. The formation of the nonuniform periodic magnetic structure is observed without changes in the film topography. The spatial symmetry of the magnetic force microscopy signal and the specific shape of magnetization curves indicate the formation of the magnetic bubbles or magnetic vortices within the irradiated spot depending on the irradiation dose. The experimental data are in a good agreement with micromagnetic simulations of the system.

We consider the thermodynamic and kinetic properties of Nickel as an example of transition metal in two-temperature state ($T_e{\mathrm{\gg T}}_i$ ,) produced by femtosecond laser heating. Our physical model includes essential processes induced in metals by ultrafast laser energy absorption. Specifically, the electron-ion collision frequency was obtained from recent high-temperature measurements of electrical conductivity and electron-electron screened Coulomb scattering was calculated by taking into account s-s and s-d collisions. In addition, chemical potential, energy, heat capacity, and pressure were obtained from first-principles density functional theory calculations. This model was implemented in two-temperature hydrodynamic code (2T-HD) and combined with molecular dynamics (MD) to determine strength of molten Ni at high strain rates ${\text{∼10}}^8{\text{-10}}^9{\mathrm{s}}^{\text{−1}}$ under conditions of femtosecond laser ablation experiments. The simulated ablation threshold, which depends on material strength, was found to be in good agreement with our experimental measurements reported here. The combined 2T-HD/MD modeling explains the surprisingly high experimental energy density necessary to initiate ablation in Ni (the experimental crater depth in Ni is several times smaller than in Al and Au, while ablation threshold energies are similar).

The principles and features of operation of a scanning helium microscope are reviewed briefly. The measurement data on the energy distribution of secondary electrons excited by the ion beam in an Au film and on the angular dependence of the backscattered ion yield are obtained and presented for the first time. The effect of ion channeling in silicon single crystal with the (110) orientation is demonstrated.

Secondary electron energy distribution (SEED) from Mo, Ni and Pt was measured in helium ion microscope (HeIM) with semispherical retarding potential technique. For all investigated metals the energy position of the SEED maximum and the SEED width in HeIM is found to be noticeably less than in conventional scanning electron microscope and even less than predicted by previous numerical simulations. A simple analytical phenomenological function to describe the SEED shape is suggested. The reasons of the lower energy transfer efficiency in ion-electron interaction are discussed. The impact of the presence of a surface layer on SEED in HeIM is investigated and energy selective images of the specimen with hydrocarbon contaminated region are presented.