Exchange‐Coupled FePt/Fe Bilayers for Perpendicular Magnetic Recording (abstract)

Exchange‐coupled bilayers, composed of a hard and a soft layer, have been recently proposed for next‐generation recording media. They allow high anisotropy values and thus thermal stability, and exploit the hard‐soft coupling to reduce the switching field. In previous works we have realized perpendicular exchange‐coupled bilayers made of a magnetically soft Fe layer over a hard FePt(001) one, and studied the magnetic behavior as a function of Fe thickness. Here we investigate the role of the extrinsic properties in the magnetic behavior by taking into account the role of interface morphology. The hard layer morphology has been modified in a controlled way by exploiting growth temperature and in situ annealing.When FePt morphology evolves from quasicontinuous to islandlike, the magnetic regime of FePt/Fe bilayers passes from rigid magnet to exchange‐spring, as expected for an exchange‐coupling reduction. Moreover, the coercivity (HC) is strongly reduced compared with the hard layer value for all interface ...