Review Article: FePt heat assisted magnetic recording media

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 L1(0) 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 sigma(D)/D similar to 18% are possible despite elevated growth temperatures T-G = 650-670 degrees C. A 2 x reduction of < D > down to 4-5 nm and lowering sigma(D)/D < 10%-15% are ongoing efforts to increase AD to similar to 4 Tb/in.(2). X = Cu similar to 10 at. % reduces the Curie temperature T-C by similar to 100K below T-C,T-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 similar to 0.96 and high chemical order S > 0.90 result in magnetic anisotropy K-U similar to 4.5 x 10(7) erg/cm(3), and only 25% below the FePt single crystal value K-U = 6.6 x 10(7) erg/cm(3) has been achieved in 7-8 nm diameter grains. Switching field distributions depend on anisotropy field (H-K) distributions, which are currently of the order of Delta H-K/H-K similar to 10% (Delta H-K similar to 10-12 kOe, H-K similar to 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. (C) 2016 Author(s).