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Perpendicular recording media for hard disk drives
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Image of FIG. 1.
FIG. 1.

Illustration of grains, the randomness of easy-axis orientations and the bit boundary.

Image of FIG. 2.
FIG. 2.

Epitaxial growth of Co(110) planes on Cr(200) planes in longitudinal recording medium.

Image of FIG. 3.
FIG. 3.

The randomness of easy axis orientation: (a) three-dimensional (3D) random, (b) two-deminsional (2D) random, (c) oriented media, and (d) ideal orientation.

Image of FIG. 4.
FIG. 4.

Trend of and as a function of areal density in longitudinal recording technology.

Image of FIG. 5.
FIG. 5.

Bit boundary in longitudinal recording for three cases: (a) decoupled grains with negligible exchange coupling, (b) magnetic clusters with moderate exchange coupling, and (c) domain wall motion reversal mechanism.

Image of FIG. 6.
FIG. 6.

Illustration of grains in magnetic recording media (a) with narrow grain boundary, (b) with broader nonmagnetic grain boundary, and (c) illustration of a grain with a magnetic core and nonmagnetic grain boundary.

Image of FIG. 7.
FIG. 7.

The energy levels (for different applied fields) associated with a magnetic particle that switches coherently (as per the Stoner-Wohlfarth model).

Image of FIG. 8.
FIG. 8.

Illustration of magnetic charges and the associated demagnetizing fields for longitudinal and perpendicular recording (a) thin film, (b) low density, and (c) high density. The arrows indicate the direction of demagnetizing field. Block arrows are used to show the higher strength of demagnetizing field.

Image of FIG. 9.
FIG. 9.

Writing process in (a) longitudinal and (b) perpendicular recording. In perpendicular recording technology, the medium is virtually placed in the pole gaps between the head and the mirror image in SUL.

Image of FIG. 10.
FIG. 10.

Different functional layers of perpendicular recording medium with approximate thickness (layers are not to scale).

Image of FIG. 11.
FIG. 11.

Illustration of 180° domain formation in SUL and an enlarged view of a transition.

Image of FIG. 12.
FIG. 12.

Schematic view of different ways in which the SUL can be exchange biased in the radial direction as described in (a) Ref. 119 , (b) Ref. 16 , and (c) Ref. 121 .

Image of FIG. 13.
FIG. 13.

Magnetization of two layers of antiferromagnetically coupled SUL during the writing and reading (remanence).

Image of FIG. 14.
FIG. 14.

(Color online) Mapping of noise pattern of SUL with a spin-stand and a read-write head: (a) single SUL and (b) antiparallelly coupled SUL.

Image of FIG. 15.
FIG. 15.

Illustration of (a) typical layers of current perpendicular recording media, (b) heteroepitaxial growth, and (c) design that involves dual Ru layers.

Image of FIG. 16.
FIG. 16.

(Top) Illustration of remanence magnetization state of grains of perpendicular media after it was saturated with a field into the plane. (a) Grains with a lower anisotropy constant show a reversal with remanent magnetization out of the plane showing instability. (b) Grains with a higher anisotropy constant show stable magnetization. (Middle) Illustration of hysteresis loops of the respective media that show (c) a positive and (d) a negative (bottom) hysteresis loop with relevant parameters.

Image of FIG. 17.
FIG. 17.

TEM planar view of a typical perpendicular recording medium.

Image of FIG. 18.
FIG. 18.

Illustration of (a) media layer structure and (b) epitaxial growth of Ru and recording layer on crystalline FeCo SUL.

Image of FIG. 19.
FIG. 19.

Layer structure of media in (a) conventional perpendicular media with dual Ru layers and (b) advanced media with a magnetic intermediate layer.

Image of FIG. 20.
FIG. 20.

TEM planar view of grains in (a) RuCr intermediate layer and (b) RuCr-oxide intermediate layer.

Image of FIG. 21.
FIG. 21.

Grain size distribution in media deposited (a) RuCr intermediate layer and (b) RuCr-oxide intermediate layer.


Generic image for table
Table I.

Properties of some soft magnetic materials.

Generic image for table
Table II.

List of intermediate layers (ILs) in the earlier days of perpendicular recording.

Generic image for table
Table III.

Approximate requirements for high-density recording media and how they are related to the recording performance (in current products and for approximately areal density).


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Perpendicular recording media for hard disk drives