L10 FePt films with high T capping layer for Heat Assisted Magnetic Recording (HAMR)

Abstract The effect of a 1.5 nm thick CoX layer (CAP) of high Curie temperature T C , deposited on top of an L1 0 Fe 50 Pt 50 layer (MAG) on the properties of the MAG/CAP bilayer is investigated. Two series of samples are studied: “w/o CAP” are single MAG layers of thickness in the 3.8–10.5 nm range and “w/CAP” are MAG/CAP bilayers of MAG thickness in the 3.8–10.5 nm range and 1.5 nm CAP. For both series, magnetization reversal is investigated at T RT  = 300 K and is shown to be coherent rotations up to a MAG thickness threshold of t cr  ∼ 7.5 nm and incoherent, domain-wall mediated, above t cr . The dependence of d H RC / d T T = T C , where H RC is the remanence coercivity, on the MAG thickness indicates t cr is poorly dependent on temperature from T RT up to the MAG T C . The MAG T C distribution, of average 〈 T C 〉 and standard deviation σ TC , is evaluated for both series. The results indicate 〈 T C 〉 is higher and σ TC /〈 T C 〉 is lower w/CAP than w/o, particularly at low MAG thicknesses. This behavior is interpreted as a consequence of spin exchange hardening in the MAG layer in the proximity of the MAG/CAP interface. For the w/CAP case, the saturation field of the Thermoremanent magnetization exhibits a non-motononic dependence on the MAG thickness, displaying a maximum. This behavior indicates the CAP assists the applied field to set the MAG layer magnetization during a HAMR process, the assist effect becoming more efficient the lower is the MAG thickness.