Dynamic magnetic information storage or retrieval – Record medium – Disk
Reexamination Certificate
1999-03-19
2003-02-11
Nguyen, Hoa T. (Department: 2652)
Dynamic magnetic information storage or retrieval
Record medium
Disk
Reexamination Certificate
active
06519114
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a magnetic data storage system, and more particularly, to magnetic storage media employed in the data storage system having textured zones.
Conventional data storage systems, such as a disc drive, employ magnetic storage media, such as a disc, to store large amounts of data in magnetic form. Typically, one or more media are rotated on a spindle relative to a magnetic head. The magnetic head is used to read or write data to or from the storage medium.
A typical contact start and stop (CSS) operating regime commences when the head begins to slide against the surface of the medium as the medium rotates. Once a suitable speed is achieved, the head floats at a predetermined distance from the surface of the medium due to an aerodynamic lift force caused by airflow generated between the magnetic head and the storage medium.
The magnetic head typically includes a slider having an air bearing surface. During reading and recording operations, the head is maintained at a controlled distance from the recording surface. The head is supported on the air bearing surface as the medium rotates such that the head can be freely moved in both the circumferential and radial directions allowing data to be recorded onto or read from the medium. When the data storage system stops, the rotational speed of the medium decreases, and the head again begins to slide against the surface of the medium, and eventually stops in contact with a surface of the medium. Thus, the head contacts the recording surface whenever the medium is stationary, accelerated from the stop, during deceleration, and prior to completely stopping. This process continues each time the data storage system is operated.
The distance between the head and the storage medium during operation is minimized to increase the storage density of the storage system. Generally, a smooth recording surface is preferred, to permit the head and the medium to be positioned in close proximity. This results in a more consistent behavior between the air bearing surface of the magnetic head and the storage medium. However, if the head surface and recording surface are too flat, stiction and friction during the start-up and stopping phases may occur. This may cause wear to the head and recording surfaces and eventually lead to “head crash”.
One technique to avoid stiction is to roughen the recording surface of the magnetic storage medium to reduce the friction between the head and the medium. This is known as “texturing.” Typical texturing techniques involve polishing the surface of a medium substrate to provide a texture thereon-prior to subsequent deposition of layers, such as an underlayer, a magnetic layer, a protective overcoat, and a lubricant topcoat. The textured surface on the substrate is substantially formed in the subsequently deposited layers.
To achieve higher recording densities, greater requirements are imposed on the magnetic storage medium in terms of coercivity, stiction, and narrow track size. In addition, increasingly high density and large capacity magnetic media require increasingly smaller fly heights. The term fly height generally refers to the distance between the storage medium and the head as the head flies over the recording surface of the medium. Reduced fly heights also pose difficulty when using texturing techniques because of the increased probability of contact between the head and the medium.
Several problems exist with known texturing techniques. For example, it is extremely difficult to provide a clean textured surface due to debris formed by mechanical abrasions during mechanical texturing. The surface becomes scratched during mechanical operations, which contributes to poor glide characteristics and higher defects. In addition, various desirable manufacturing substrates are difficult to process by mechanical texturing.
Alternatively, laser texturing has been employed, and includes a laser light being focused on an upper surface of a non-magnetic substrate. Conventional laser texturing techniques have previously been applied to metal-containing substrates. Such substrates, however, exhibit a tendency toward corrosion, and are relatively fragile, thereby limiting their utility. On the other hand, glass and glass-ceramic substrates may be employed. However, it is extremely difficult to provide an adequate texture on a glass or glass-ceramic substrate.
Current laser texture designs include a matrix of isolated bumps with specified circumferential and radial pitches. The bump height is tightly controlled to give a uniform support to the head during the rest position. However, the regular pattern of bump arrangements is known to cause a resonance excitation. Resonance excitation is the situation where fluctuations occur in the fly height during take off and landing of the head relative to the medium. The periodic pattern of the bump matrix excites the head when it flies close to the texture. When an excitation frequency matches one of the resonance frequencies of the data storage system, enhanced head vibration results and head crash is more common.
One technique for reducing resonance excitation includes reducing the texture excitation strength at the operating resonance frequencies. The bump locations in the texture zone may be partially randomized. This results in a texture pattern that has a wide spectrum of excitation frequencies. However, the above configuration does not permit significantly lower fly heights to be achieved. This is because the resonance excitation is not adequately minimized.
Therefore, a-need exists for a storage media having textured surfaces for contact with magnetic storage heads that minimizes resonance excitation between the magnetic head and the storage medium.
SUMMARY OF THE INVENTION
In one aspect, the invention is directed to a method for manufacturing a magnetic recording medium that includes texturing a surface of the medium to form a texture zone. The texture zone includes a plurality of protrusions, where each of the protrusions is separated by a circumferential pitch. The circumferential pitch is chosen to move the excitation frequencies of the texture zone away from the resonance frequencies of a magnetic head.
Implementations of the invention include one or more of the following. The diameter of each of the protrusions may be between 1 &mgr;m and 20 &mgr;m. The circumferential pitch may vary with the diameter of the plurality of protrusions. The texturing step includes forming the texture zone by laser texturing. The plurality of protrusions may be formed to create a plurality of periodic texture features. The periodicity of the textured features may correspond to the circumferential pitch.
In another aspect, the invention is directed to a data storage system that includes a magnetic storage medium having a texture zone. A magnetic head is positioned relative to the storage medium. The texture zone is formed from a plurality of protrusions in which each of the protrusions is separated by circumferential pitch. The circumferential pitch is chosen to move the excitation frequencies of the texture zone away from the resonance frequencies of the magnetic head.
Implementations of the invention include one or more of the following. The data storage system may include a slider having a first surface and a second surface. An air bearing surface may be formed on the second surface, and a transducer assembly may be formed proximate the air bearing surface to read or write data to or from a plurality of data tracks on the medium. The medium may include a plurality of layers formed on a surface of the medium.
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Kuo David Shiao-Min
Wang Li-Ping
Yao Wei Hsin
Fish & Richardson P.C.
Nguyen Hoa T.
Seagate Technology Inc.
Tianjie Chen
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