Improvement of chemical ordering of FePt (001) oriented films by MgO buffer layer

Abstract

Chemically ordered L10 FePt layer was obtained at temperature as low as 280°C by in situ heating by using MgO buffer layer on CrRu (200) underlayer. The chemical ordering and magnetocrystalline anisotropy, Ku, increased with increasing deposition temperature from 280to400°C. The out-of-plane coercivity Hc⊥ also increased significantly from 2.7to9.0kOe. All the films showed perpendicular anisotropy. The reason for the increase in the coercivity was investigated by reducing the thickness of the FePt layer to 4nm and varying the thickness of the MgO buffer layer at 1, 2, and 4nm. Well isolated FePt islands were formed. When the MgO layer was 1nm, the Hc⊥ of the 4nm FePt layer was as high as 12kOe. However, it reduced to 6.3kOe when the MgO was 4nm. The change in Hc⊥ was due to the improved chemical ordering and thus higher magnetocrystalline anisotropy.