Structural investigation of ultrathin Pt/Co/Pt trilayer films under EUV irradiation

Trilayer systems containing ultrathin (3 nm) cobalt layer grown on 5 nm thick Pt buffer layer and covered with 3 nm thick Pt cap layer grown at room temperature by molecular beam epitaxy on the Al2O3(00.1) substrate have been irradiated by nanosecond extreme ultraviolet light pulses. It was previously evidenced that light irradiation induced irreversible change of direction of magnetization in such nanostructures. In order to understand the reasons of such behavior the structural studies with the use of X-ray diffraction and transmission electron microscopy of the as-grown and irradiated samples have been done. It was found that irradiation leads to intermixing of cobalt with platinum giving rise to creation of Pt1−xCox disordered alloy. The methodology of determination of the strain state of the layers, relaxed lattice parameter of the unit cell and the composition of Pt1−xCox alloys has been developed and described in details. The results of structural studies of the as grown Pt/Co/Pt nanostructures as well as those modified by irradiation are presented in this paper.