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Magnetic media for heat-assisted magnetic recording

Keywords:

V.G. Shadrov – Ph.D. (Phys.-Math.), Leading Research Scientist, Scientific-Practical Materials Research Centre A.V. Boltushkin – Ph.D. (Phys.-Math.), Leading Research Scientist, Scientific-Practical Materials Research Centre A.E. Dmitrieva – Junior Research Scientist, Scientific-Practical Materials Research Centre E-mail: nemtsevich@ifttp.bas-net.by


Driven by 40% annual growth in the need for worldwide data storage, increase in areal density is crucial for the hard disc drive industry. A signal-to-noise, thermal stability, and writability tradeoff limits the ability to continue to scale traditional magnetic recording technology to higher storage densities. As a solution exchange-coupled media, heat-assisted magnetic recording (HAMR) and bit patterned magnetic recording are proposed. In the present paper key HAMR media parameters, magnetic materials used as well as alternative high anisotropy materials and media designs are analyzed. It has been shown that heat-assisted magnetic recording technology based on local heating the recording media for the media coercivity decreasing allows significant smaller thermally stable grains in ordered L10 FePt based alloys (3…4 nm) in comparison with modern perpendicular Co alloy based media (7…9 nm). In particular, granular L10 FePtCuAg-C (5…8 at.% Cu, 30…50 at.% C) medium is proposed as optimal one. In addition to alloy additives for recording temperature decreasing, alternative HAMR media designs are proposed, for example, exchange-spring FePt/FeRh structure and exchange-coupled multilayer structure with different layer Curie temperatures. Upon heating FePt/FeRh structure beyond the Neel temperature, FeRh becomes ferromagnetic and assists the switching of the hard FePt layer via an exchange-spring effect. Besides general requirements concerning grain size and form, grain size and switching field distributions, for achieving high signal-to-noise and increasing areal density it is also necessary to optimize thermal properties of magnetic layer and optical transducer parameters. The analysis made allows to conclude that HAMR media with areal densities greater than 1 Tb/inch2 are possible in 2016-2020. Extensions beyond 10 Tb/inch2 will likely require the combination of HAMR and bit patterned magnetic recording technologies.
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