Abstract
Heat-assisted magnetic recording (HAMR) media status, requirements, and challenges to extend the areal density (AD) of magnetic hard disk drives beyond current records of around 1.4 Tb/in.2 are updated. The structural properties of granular high anisotropy chemically ordered L10 FePtX-Y HAMR media by now are similar to perpendicular CoCrPt-based magnetic recording media. Reasonable average grain diameter ⟨D⟩ = 8–10 nm and distributions σD/D ∼ 18% are possible despite elevated growth temperatures TG = 650–670 °C. A 2× reduction of ⟨D⟩ down to 4–5 nm and lowering σD/D < 10%–15% are ongoing efforts to increase AD to ∼4 Tb/in.2. X = Cu ∼ 10 at. % reduces the Curie temperature TC by ∼100 K below TC,bulk = 750 K, thereby lowering the write head heat energy requirement. Multiple FePtX-Y granular layers with Y = 30–35 vol. % grain-to-grain segregants like carbides, oxides, and/or nitrides are used to fully exchange decouple the grains and achieve cylindrical shape. FePt is typically grown on fcc MgO (100) seedlayers to form well oriented FePt (002). A FePt lattice parameter ratio c/a ∼0.96 and high chemical order S > 0.90 result in magnetic anisotropy KU ∼ 4.5 × 107 erg/cm3, and only 25% below the FePt single crystal value KU = 6.6 × 107 erg/cm3 has been achieved in 7–8 nm diameter grains. Switching field distributions depend on anisotropy field (HK) distributions, which are currently of the order of ΔHK/HK ∼ 10% (ΔHK ∼ 10–12 kOe, HK ∼ 10–11 T) at room temperature. High thermal conductivity heat sink layers, including Ag, Au, Cu, and Cr, are used to optimize the cooling rate and maximize the down- and cross-track thermal gradient, which determines the achievable track density.
Highlights
The read-back signal depends on the remanent magnetization (MR), the magnetic layer thickness (d), and the read head-disk spacing
Suess and Schrefl66 proposed an elegant way by using ECC bilayers having different Curie temperatures to overcome the current limitation in Heat-assisted magnetic recording (HAMR) recording density of about 20 Tb/in.2.67 This limit, which is given by thermally induced recording errors, can be lifted by introducing a composite structure of two exchange coupled materials
We demonstrate for a current experimental HAMR system at 1.3 Tb/in
Summary
The read-back signal depends on the remanent magnetization (MR), the magnetic layer thickness (d), and the read head-disk spacing. 060801-2 Weller et al.: Review Article: FePt heat assisted magnetic recording media. Key HAMR media layers, including a substrate, heat sink, dielectric or seed layer, the granular FePt recording layer, as well as a C-based overcoat layer.. It shows the narrow hot spot on the media, which during recording determines the bit transition and track width. Heating above the Curie temperature is needed, and recording occurs during rapid cooling on the trailing edge of the temperature profile.
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