Stock material or miscellaneous articles – Magnetic recording component or stock – Thin film media
Reexamination Certificate
2006-03-09
2009-06-23
Bernatz, Kevin M. (Department: 1794)
Stock material or miscellaneous articles
Magnetic recording component or stock
Thin film media
C428S828100, C360S125020, C360S135000
Reexamination Certificate
active
07550210
ABSTRACT:
A perpendicular magnetic recording medium has an “exchange-spring” type magnetic recording layer (RL) formed of two ferromagnetic layers with substantially similar anisotropy fields that are ferromagnetically exchange-coupled by a nonmagnetic or weakly ferromagnetic coupling layer. Because the write head produces a larger magnetic field and larger field gradient at the upper portion of the RL, while the field strength decreases further inside the RL, the upper ferromagnetic layer can have a high anisotropy field. The high field and field gradient near the top of the RL, where the upper ferromagnetic layer is located, reverses the magnetization of the upper ferromagnetic layer, which then assists in the magnetization reversal of the lower ferromagnetic layer. Because both ferromagnetic layers in this exchange-spring type RL have a high anisotropy field, the thermal stability of the medium is not compromised. The medium shows improved writability, i.e., a low switching field, as well as lower intrinsic media noise, over a medium with a conventional single-layer RL.
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Berger Andreas Klaus
Do Hoa Van
Fullerton Eric E.
Ikeda Yoshihiro
Lengsfield, III Byron Hassberg
Bernatz Kevin M.
Berthold Thomas R.
Hitachi Global Storage Technologies - Netherlands B.V.
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