Composite magnetic films for optically assisted magnetic recording (rapid thermally annealed FePt crystalline grains/magneto optical recording film)

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In this study, we discussed the composite magnetic recording media, consisting of FePt grain under layer with TbFeCo continuous layer, as high density optically assisted recording media over 1 Tbit/in^2. Due to its high magnetic anisotropy K_u and the capability of forming small grains, FePt is a leading candidate for high density magnetic recording media that are preferable to overcome the thermal fluctuation of small magnetic grains. FePtX (X=Cu, Ni) prepared by Rapid Thermal Annealing (RTA). To increase areal packing density of FePtX grains, a SiO_2 Substrate having self-organized nano-pores was used as a nano-template. Main results were followings1) Fabrication of nano-dent array substrate by self-assemble methodWe succeeded to fabricate SiO_2 film having highly ordered nano-pores inside, and found that the dilution of a solvent with ethanol is effective to thinning the film thickness preparing by spin coring method.2) Decrease of the Curie temperature of FePt by Cu or Ni dopingSubstituting Cu or Ni for some of the Fe is expected to reduce the K_u i. e. Curie temperature T_c (FePt, T_c=500℃ at room temperature). We fabricated well isolated FePtX(X=Cu, Ni) particles by RTA, and confirmed the doping effect to reducing Curie temperature. Deferent content dependence was found in each element.3) Micro-magnetic simulations of domain shape incomposite magnetic recording mediaSimulated result of composite magnetic film consisting of FePt grains under layer and TbFeCo continuous layer shows tiny domain could be formed (domain diameter 22 nm at the TbFeCo surface). Even the spacing between each grain decreased less than the theoretical domain wall width, FePt particles act as domain pinning sites of TbFeCo layer.