Simulation of defects and composition after Ga+ irradiation of ultrathin Pt/Co/Pt film

Theoretical studies of the collision intermixing and defects creation processes of irradiated ultrathin Pt/Co/Pt films by 30 keV Ga+ are presented. First, in order to investigate the influence of the Ga ions, with ion fluence ranging between 1014 and 5·1016 ions/cm, on the composition of the film and the sputtering yield TRIDYN simulation is employed. Second, the relaxation of defects created during irradiation is estimated by means of the Lattice Kinetic Monte Carlo Ising model, which is subsequently applied after each collision cascade. According to our theoretical results ion fluence has a strong impact on the erosion velocity and intermixing processes that take place at the interface. Due to the nuclear energy losses of the implanted ions, changes in the material composition at the interface and the spin reorientation transition from the in-plane to out-of-plane magnetization state is observed. Moreover, the so-called swelling effect, which originates from the strain relaxation of the irradiated films, gives rise to an increase of the magnetic anisotropy. However, the strain relaxation can be strongly non-uniform in the implanted square area providing a mixture of patches with in-plane or out-of-plane anisotropy. Experimentally observed irradiation induced phenomena is fairly well described in the frame of our simulations.