Deposition temperature mediated tunable tilt angle magnetization in Co–Pt/Ni81Fe19 exchange springs

Abstract

Abstract In this study, we investigate the effect of deposition temperature of Co–Pt fixed layer, T d,CoPt (150, 250 and 350 °C) on the tilt angle magnetization ( θ M ) of Ni 81 Fe 19 -layer grown at room temperature (RT) and at different thicknesses ( t NiFe =0, 1.0, 2.5 and 4.0 nm) in Co–Pt( T d,CoPt )/NiFe( t NiFe ) exchange springs. The magnetic studies demonstrated a strong perpendicular magnetic anisotropy (PMA) for the equi-compositional ordered Co–Pt layer grown on glass substrate using the film sequence: Ta(20 nm)/Pt(20 nm)/CoPt(5 nm), regardless of T d,CoPt . The PMA can be retained with the addition of a 4-nm NiFe layer on the top when T d,CoPt ≥250 °C. In contrast, relatively a thin layer of Ni–Fe (2.5 nm) can destroy the perpendicular exchange-spring behavior if the Co–Pt layer is deposited at RT. Using 3-D micromagnetic simulation, the interfacial exchange coupling strength ( A ij ) between the Co–Pt and NiFe-layers was estimated and the A ij value is found to increase rapidly when T d,CoPt is increased from RT to 300 °C. Besides, the magnetization tilted angle ( θ M ) of NiFe can be easily tuned from completely out-of-plane to almost 60° when t NiFe =4.0 nm. Through this study, it is demonstrated that the θ M of NiFe-layer can be tuned by not only altering the t NiFe ; but also by varying the T d,CoPt .