Stock material or miscellaneous articles – Circular sheet or circular blank – Recording medium or carrier
Reexamination Certificate
1997-11-10
2001-06-19
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Circular sheet or circular blank
Recording medium or carrier
C428S336000, C428S632000, C428S634000, C428S634000, C428S634000, C428S634000, C428S300400, C427S128000, C427S123000, C427S130000, C360S100100, C360S135000
Reexamination Certificate
active
06248416
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
BACKGROUND OF THE INVENTION
The present invention is directed generally to thin films, magnetic recording media, transducers and devices incorporating the films and, more particularly, to thin films promoting highly oriented cobalt or cobalt alloy magnetic layers for use in magnetic recording media and transducers.
There is an ever increasing demand for magnetic recording media with higher storage capacity, lower noise and lower costs. To meet this demand, recording media have been developed with increased recording densities and more well-defined grain structures that have substantially increased the storage capacity, while lowering the associated noise of the recording media. However, the rapid increases in recording densities over the last two decades, combined with the proliferation of personal computers have only served to fuel the demand for even higher storage capacity recording media having lower noise and cost.
Computational and data manipulation devices are being used in a rapidly expanding number of applications. Examples of these include supercomputers, personal desk top and portable laptop computers, file servers, personal data assistants, data collection devices, article tracking systems, video recorders, digital audio recorders, and even telephone answering machines. A common architectural feature is that they all have a central processing unit, input-output interfaces, various levels of temporary memory, and usually some form of permanent data storage device. The distinguishing characteristic of the permanent data storage device is that the information remains intact even if the electrical power is lost or removed. Data are stored on permanent data storage devices either optically or magnetically. The more commonly used data storage devices are based upon magnetic materials which are erasable and re-recordable. Common to all magnetic data storage devices are record and read transducers, a magnetic medium upon which to store the data, and a mechanism to position the medium or the transducers relative to one another.
Some of the more common permanent data storage devices include the floppy disk drive, the hard disk drive, and the magneto-optic disk drive in which data are stored in magnetic bits in segmented circular tracks. The magnetic medium is rotated and the transducers are stationary or moved radially to read or write data at a location on the medium.
Likewise, the magnetic medium is sometimes constructed as a tape or a sheet and is transported linearly while the transducers may be stationary, moved transversely across the moving medium, or even moved in a helical arc relative to the medium. Also, in the future it is conceived that very large amounts of data may be stored on physically very small formats where the medium or the transducers are moved in two dimensional Cartesian coordinates or arc motions relative to each other to access the data.
Historically, the transducers for many of the non-optical magnetic data storage systems have been inductive magnetic heads used for recording data by magnetizing the medium in a particular direction and for reading the data by detecting the direction of the magnetized medium. More recently, an inductive magnetic head is used for recording the data pattern while a magnetoresistive sensor is used for reading the data. In many of the magneto-optical storage devices an integral part of the record transducer is a component which generates a magnetic field at the medium surface while the surface is heated by using an optical source. The medium magnetization then assumes the magnetic orientation of the field generated by the record transducer when the medium cools. In some systems this orienting field is provided by an adjancent magnetic material.
Due to the physical size, efficiency and orientation of the record and read transducers the magnetic medium is generally magnetized in a preferred orientation. Hence, in almost all magnetic data storage media it is desired to orient the magnetic media in a direction to match the operational orientation of the recording and playback transducer. In addition, magnetic materials generally will magnetize more easily in a preferred orientation or orientations, along what are known as a magnetically easy axis or axes.
Magnetic properties, such as coercivity (H
c
), remanant magnetization (M
r
) and coercive squareness (S*), are crucial to the recording performance of the medium. These magnetic properties are primarily dependent on the microstructure of the film for a fixed composition. For thin film longitudinal magnetic recording media, the magnetized layer preferably has uniaxial crystalline anisotropy and a magnetization easy axis directed along the c-axis and predominately in the plane of the film (i.e, in-plane). The predominate crystallographic orientation of a layer is known as the crystallographic texture, or texture, as used herein, as opposed to the use of the term “texture” to describe the mechanical roughness of a surface. That is, a crystal having a surface and a crystallographic plane parallel to the surface would be said to have a texture described by a direction vector orthogonal to the surface. Usually, the better the in-plane c-axis orientation, the higher the coercivity of the magnetic layer used for longitudinal recording. High coercivity is required to achieve a high remanence. Likewise, for perpendicular magnetic recording media, the desired crystalline structure of the Co alloys is hexagonal close packed (“hcp”) with the uniaxial anisotropy and crystalline c-axis perpendicular to the film plane.
It is generally desirable to align the magnetically easy orientation of the medium with the orientation of the transducers. By aligning the orientations of the medium and the transducers, a data bit can be recorded with a lower energy transducer field and the ability to more easily magnetize the medium provides for a more strongly magnetized portion of the medium. The combination of these two effects allows a data bit to be recorded to and read from a more localized, yet more highly magnetized, portion of the medium. In other words, by aligning the relative magnetic orientations of the transducers and the medium, increased recording densities and storage capacities can be achieved. This results in a higher performance data storage device by allowing more data to be stored in a smaller area on the media. It also results in a lower cost per data bit and possibly lower cost storage devices, as fewer components are required to build an equivalent or larger capacity storage device. In many cases it also results in a decreased access time to reach a particular piece of stored data since the physical size of the storage system is smaller.
In the rotating storage devices it is desirable that the orientation of the medium be either random parallel to or constant in relation to the circumferential direction in the plane of the medium or that the orientation be perpendicular to the medium surface. In each of these orientations the relative orientations of the magnetic medium and the transducers does not vary as the medium is rotated relative to the transducers. Variations in the relative orientations of the medium and the transducers results in variations in the recording and reading of signals, which is known as signal modulation.
For floppy disks and most hard disks the orientation is nearly random in the plane of the medium. However, rotating magnetic media often have some small degree of orientation along the record track direction due to the mechanical roughness of the substrate surface. For perpendicular magnetic media, the orientation must be well oriented perpendicular to the media plane to match the field orientation of the record and read transducers. In magneto-optical recording, the magneto-optical Faraday effect, or Kerr effect, is far larger when the light propagates parallel to the magnetization direction. Because the light is usually delivered perpendicular to the medium surface, it is desired that the magnetic
Gong Heng
Lambeth David N.
Laughlin David E.
Yang Wei
Ziou Jie
Carnegie Mellon University
Kiliman Leszek
Kirkpatrick & Lockhart LLP
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