Strain in Al/Co/Pt(111) sandwich with peculiar magnetic anisotropy properties

Pt/Co/AlOx trilayer is largely studied due to its strong perpendicular magnetic anisotropy (PMA). While previous studies have focused on the role of Co/Al interface oxidation, recent findings suggest that the strain induced by the Al layer on the Co lattice can tune the PMA. Our measurements on a Pt(8)/Co(0.9)/Al(tAl) wedge show a striking double sign change of the magnetic anisotropy as a function of thickness and oxidation of the Al layer, with an increase of PMA when the Co/Al interface becomes metallic. This suggests that strain might govern the observed anisotropy changes. We aim to highlight a variation of the in-plane lattice parameter of the Co layer vs. Al thickness and oxidation degree of the Co/Al interface and relate it to our PMA results. We propose to carry out in-situ measurements on a sample grown epitaxially on a Pt(111) crystal. The in-plane lattice constant of Al/Co/Pt(111) films with Co as thin as 4 ML will be measured by glancing angle x-ray diffraction.