Role of interface morphology in the exchange-spring behavior of FePt/Fe perpendicular bilayers

The role of interface morphology in the magnetic behavior of FePt/Fe exchange-coupled systems has been considered. Hard/soft bilayers with different interface morphologies were obtained by depositing Fe thin layers on FePt epitaxial layers with different morphologies, but all with a high degree of L10 ordering and high coercivity. It was found that the hard/soft coupling can be tuned by changing the FePt morphology, allowing tailoring of the hysteresis loops and modification of the magnetic regime at a fixed Fe thickness (from Rigid Magnet to Exchange-Spring magnet). Remarkably, all bilayer series showed a drastic reduction in coercivity with increasing Fe thickness to 3.5 nm (μ0HC ⩽ 1.1 T).