Investigation of magnetic coupling in FePt/spacer/FePt trilayers

The effect of different spacer materials (MgO, W, and Pt) on the magnetic coupling in FePt/spacer/FePt trilayers has been carefully investigated. MgO results in magnetically coupled FePt layers with perpendicular magnetic anisotropy (PMA); W gives rise to a magnetically coupled system consisting of layers with PMA and in-plane magnetic anisotropy whereas Pt results in magnetically decoupled FePt layers with PMA. The trilayer microstructure is essential for explaining the obtained results. The growth mode of the top FePt layer is strongly affected by the underlying non-magnetic spacer, with occurrence of different morphologies; in particular, L10 FePt islands grow on MgO, a continuous FePt layer with fcc crystal structure is obtained on W, whereas a continuous layer with L10 structure is observed when the top layer is deposited on Pt.