Review Article: FePt heat assisted magnetic recording media

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.

Finite-size effects in ultrafast remagnetization dynamics of FePt

“…The fascinating field of ultrafast magnetization dynamics has developed rapidly from the first demonstration of femtosecond demagnetization [1] towards all-optical switching [2,3], magnetization reversal by ultrashort electron pulses [4] and heat-assisted magnetic recording (HAMR) [5][6][7]. Future light-based data-recording applications motivate an understanding of the fundamental light-matter-interactions in magnetic materials with nanoscale bit-dimensions, which are a key to satisfy the increasing demand for high-density information storage technology.…”

Effect of an Additional Ag Layer on Formation of the Ordered $L1_0$-FePt Phase in Ag (0; 7.5 nm)/Fe$_{50}$Pt$_{50}$ (15 nm)/SiO$_2$ (100 nm)/Si(001) Films

“…Такими матері-ялами є стопи із впорядкованою структурою L1 0 , наприклад, FePt. Ці стопи мають високі магнетні властивості, зокрема високу енер-гію магнетокристалічної анізотропії впорядкованої фази L1 0 -FePt (K U = 7⋅10 6 Дж/м 3 ), що забезпечує стабільність зберігання інформа-ції, при малому розмірі зерна [1].…”

“…Для уможливлення використання плівок на основі FePt необхід-но вирішити певні технологічні задачі, такі як зниження темпера-тури впорядковування та контролю орієнтації зерен фази L1 0 -FePt [1]. Зниження температури впорядковування може бути досягнуто впливом багатьох чинників, у тому числі фізико-технологічних па-раметрів одержання [3,4], за рахунок впливу підкладинки [5], до-давання легувальних елементів [4,[6][7][8], використання багатошаро-вих структур [9].…”

Synthesis of a High-Coercivity FePt–Ag Nanocomposite Magnet via Block Copolymer-Templated Self-Assembly

“…Magnetic recording media are composed of magnetic thin films consisting of magnetically isolated crystallites [1][2][3][4][5][6]. Increasing the recording density requires a reduction in the medium area for a single bit, which in turn necessitates a proportional decrease in the volume of the magnetic particles constituting the medium.…”