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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 hDi=8-10 nm and distributions rD/D∼18% are σpossible despite elevated growth temperatures TG=650-670°C. A 2x reduction of hDi down to 4-5 nm and lowering rD/D<10%-15% are ongoing efforts to increase AD to ∼4 Tb/in.2. X=Cu∼10 at. % reduces the Curie temperature TC by ∼100K 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 x 107 erg/cm3, and only 25% below the FePt single crystal value KU=6.6 x 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 DHK/HK∼10% (DHK∼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. [ABSTRACT FROM AUTHOR]

The write field requirements in heat-assisted magnetic recording (HAMR) using FePt media are studied using an atomistic model. Langevin dynamics simulations of laser-induced thermal demagnetization and magnetization recovery are performed on a single L \(1_\mathbf {o}\) -ordered FePt grain. We show that the minimum heat temperature for thermal overwrite of information is a cooling rate-dependent temperature \(\boldsymbol T\!_\mathbf {o}\) , larger than the Curie temperature of the grains. If \(\boldsymbol T\!_\mathbf {o}\) is exceeded, memory effects can be neglected in HAMR since the characteristic pulse time is long compared with the mean first passage time of thermal demagnetization. The minimum write field \(\boldsymbol H_{\boldsymbol {\rm w}}\) to attain sufficiently high thermoremanence \(\boldsymbol M\!_{\boldsymbol Z}\boldsymbol =\mathbf {0.9}\boldsymbol M\!_{\boldsymbol S}\) is then independent of the heating process. We study the variation of \(\boldsymbol H_{\boldsymbol {\rm w}}\) with cooling rate, damping, field orientation, and grain size \(\boldsymbol L\) , and explore the phase space of the parameters \(\boldsymbol H\) , \(\boldsymbol T\) , and \(\boldsymbol L\) , also resulting in thermal stability of the recorded information during storage. [ABSTRACT FROM AUTHOR]

This paper discusses heat-assisted magnetic recording (HAMR) media requirements and challenges for areal densities (AD) beyond 1~\Tb/in^2. Based on recent roadmap discussions the focus is primarily on granular chemically ordered L1_0 FePtX-Y-perpendicular media with reduced average grain size down to \langleD\rangle=3\-5~\nm relative to current CoCrPt based perpendicular magnetic recording (PMR) media with average grain size \langleD\rangle=7\-9~\nm. In HAMR media the combination of thermal conductivity and Curie temperature TC determines the required laser power during recording. Key challenges are sigma variations of D and TC which need to be reduced to \sigmaD/\rm D\sim 10\-15\% and \sigmaTC/\rm TC\sim 2\%. In addition AD is limited by switching field distribution (SFD) and thermal spot size. The key goal going forward is to optimize heads, media, head-media-spacing (HMS) and read-back channel technologies to extend AD to 4~\Tb/in^2 and beyond. [ABSTRACT FROM PUBLISHER]

Highly chemically ordered L10 FePtX-Y nano-granular films with high perpendicular magnetic anisotropy are key media approaches for future heat-assisted magnetic recording (HAMR). They are sputtered at elevated temperature on glass disks coated with adhesion, heat sink, and texturing layers. Adding X = Ag reduces the required deposition temperature and X = Cu lowers the Curie temperature. Current seed layers are NiTa for adhesion and heat sink and well-oriented MgO (002) layers for highly textured FePtX(002) grains surrounded by Y = carbon and/or other segregants. Magnetic anisotropies larger than 4.5 × 107 erg cm−3 and coercivities beyond 5 Tesla have been achieved. The combination of thermal conductivity and Curie temperature determines the required laser power during recording. Key goals are to optimize media, heads, head-disk-spacing, and read-back channels to extend the areal density to 1.5-5 Tb in−2. Head and media in heat-assisted magnetic recording1. LD, laser diode; TFC, thermal fluctuation control; NFT, near field transducer. 1Lidu Huang et al., 'HAMR Thermal Modeling Including Media Hot Spot', APMRC 2012. [ABSTRACT FROM AUTHOR]