Manipulating the magnetic properties and interphase coupling in FePt/Pt/Fe multilayer films by Pt spacer layer

Abstract

Single-layer FePt (10 nm) film and trilayer FePt (10 nm)/Pt (t)/Fe (3 nm)/Pt (3 nm) (t = 0 nm, 0.5 nm, 1 nm, 2 nm and 4 nm) films were prepared on MgO (1 0 0) substrate. Their cross-sectional morphologies, ordering and interphase coupling behaviors were studied in detail. The results showed that the interphase coupling stiffness (J) increased at first, and then decreased with increasing thickness of the spacer layer. An exponential fitting of J ~ t dependence was obtained for t ⩾ 1 nm. A discrepancy between experiments and exponential fitting, mainly caused by interfacial diffusion, was seen for t ⩽ 1 nm. With respect to the proposed idea of using a spacer layer to modify the interface, FePt (8 nm)/Pt (0.5 nm)/Fe (3 nm)/Pt (3 nm) anisotropic nanocomposite film exhibited the best magnetic properties, with coercivity 0.87 T and (BH)max 370 kJ m−3, accounting for 95% of the theoretical (BH)max of L10-ordered FePt phase.