Ion beam induced modifications of Pt/Co/Pt magnetic films for control of perpendicular magnetic anisotropy

Modifications of magnetic and magnetooptical properties of Pt/Co/Pt tri-layers upon irradiation with ion beam are investigated in this work. They are studied in detail as a function of the Co layer thickness, dCo (up to 5 nm), ion species (Ne+, Ar+, Ga+) the energy of ions, E (up to 30 keV) and ion fluence, F (range from 1013 to 3∙1016 ions/cm2). Modified magnetic properties are correlated with structural features of irradiated samples. Numerical simulations of in-depth atomic concentration profile and surface etching carried out by TRIDYN software complements explanation of the observed effects. MBE grown Pt/Co/Pt tri-layers display a spin reorientation transition (SRT) at a well-defined Co thickness, dSRT from out-of-plane to in-plane magnetization alignment as dCo increases. Upon ion irradiation various processes undergo: degradation of chemically sharp interfaces, formation of Co-Pt alloys and lattice strain development [1, 2]. Spread interfaces reduce perpendicular anisotropy whereas formation of the ordered alloy may strength this property. Therefore a resulting magnetic state of the sample is a product of interplay of these two opposing trends in anisotropy evolution and the sample surface etching, particularly effective for highest fluences. It is very sensitive to dCo, ion species, their energy and the ion fluence. Discussion is focused on results obtained with Ar+ ions irradiation, which is commonly used for technological processes especially for nanostructures sputtering. Set of (dCo, log F) diagrams of remanence, mr (Figure. 1), (normalized magnetization perpendicular component) measured by means of magnetooptical Kerr effect magnetometry in polar configuration (PMOKE) upon irradiation with Ar+ ions with different energies. Irradiation of the samples modifies magnetic properties in various manners depending on dCo, F and ion energy. The suppression of the dSRT with F in the range from 1013 to 1014 ions/cm2 and formation of branch(es) corresponding to str