Structure and magnetism in Co/Pt multilayers

The structure of [Co(tCo)/Pt(10 Å)]30 multilayers has been studied by x-ray absorption spectroscopy and x-ray diffraction using in-plane and out- of-plane polarized synchrotron radiation. The x-ray absorption near-edge spectroscopy shows that the Co layer is like a fcc pseudomorphic structure for tCo less than 4 Å. For tCo=10 Å, the spectra in both directions are separated and look closer to the bulk hcp Co. The extended x-ray absorption fine structure studies reveal that the Co–Pt interface of the multilayers fitted with a sharp boundary better than an interdiffusion model. The in-plane x-ray diffraction shows that the Pt layer in the multilayer possesses a 2%–3.5% compressible strain. Although the saturation magnetization Ms does not depend on tCo or interfacial roughness in any simple form, the Ms values scale quite linearly with the in-plane Pt strain. We conclude that the interfacial strain is important for the perpendicular magnetization in the Co/Pt multilayers.