Using different Mn-oxides to influence the magnetic anisotropy of FePt in bilayers with little change of the exchange bias field

Abstract

We have investigated the exchange coupling between a bottom FePt thin film layer capped withdifferent Mn-oxides. Results have shown that the magnetization reversal of the soft FePt layer isinfluenced strongly by the capped Mn-oxide layer (Mn, MnO, and Mn3O4), as revealed by theenhanced coercivities. Typical temperature dependent magnetization between zero-field cooled(ZFC) and field cooled (FC) scans was observed in the Mn-oxide (8%O2/Ar)/FePt bilayer thatexhibited a blocking temperature (TB 120 K) close to the Ne`el temperature, TN, of MnO.However, the Mn/FePt bilayer exhibited unusual temperature dependent of M vs. T, implying thatintermixing between Mn and FePt interfaces formed an AF FeMn that may have enabled a highirreversibility temperature (Tirr. 400 K) compared to almost identical ZFC and FC curves fromweaker exchange coupling between FePt and the Mn3O4 created with 21 and 30%O2/Ar depositionconditions