The Effect of the Modulation Period on the Diffusion Intermixing and Magnetic Properties Behavior of Pt/Co Thin Films Induced by Ion Pre-irradiation

The effects of modulation period and N+ ion pre-irradiation on the layers intermixing and magnetic properties modification of Pt/Co and Pt/Co/Pt/Co stacks were investigated. The correlation between structural changes, diffusion intermixing, and magnetic properties behavior was discussed as a function of ion fluence. An experimental analysis was performed using X-ray diffraction, secondary ions mass-spectrometry, and in-plane vibrating sample magnetometry characterization. The nonlinear behavior of the saturation magnetization values for the bi- and four-layered stacks was observed. Based on the results of the study, it was found that a significant increase in coercivity (498 Oe) of the four-layered stack after the pre-irradiation with a fluence of 5 × 10¹⁴ ions/cm², related to the ion-induced collisional intermixing and more pronounced formation of the structural defects. It was demonstrated that employing a significant enhancement of the formation of additional defects and intrinsic strains may stretch the crystal lattice of the A1-CoPt phase, resulting in a modification of exchange interaction between Co atoms in the thin-film composition.