Dynamic magnetic information storage or retrieval – Record medium – Disk
Reexamination Certificate
1999-04-05
2001-11-06
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Record medium
Disk
Reexamination Certificate
active
06313969
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a magnetic disk medium and a magnetic recording system, and more specifically to a magnetic disk medium and a magnetic recording system, which have main applications in computer peripheral recording equipment.
With increases in the recording capacity of computers, the recording capacity of magnetic recording systems tend to become increasingly larger. For the purpose of linear recording density increases, an important consideration is how an array of recording domains in a magnetic recording layer of a magnetic disk medium, formed by a write magnetic field generated from a magnetic head, are made minuscule.
To make the recording domains minuscule, it is particularly important to narrow the spacing between the foremost end of the magnetic head nearest to the magnetic recording layer and the magnetic recording layer, and to reduce as much as possible fringing due to a magnetic field diverging spatially from the foremost end of the magnetic head.
For noise reductions in a magnetic disk medium comprising a magnetic recording layer, the crystals of thin films are made minuscule with Br reductions, and exchange interactions among crystal grains are reduced.
It has been proposed to accomplish a medium with reductions in the transition width of magnetization and fringing upon recording by suppressing medium noise by control of crystal grains and anisotropic energy of the medium, control of orientation capability, exchange couple reductions, and use of a magnetization stabilizing structure. It has also been proposed to accomplish a thin-film magnetic disk wherein a guard band member made up of a non-magnetic material is located between adjacent recording tracks with a view to reducing side fringing of recording domains (JP-A 997419).
For the achievement of high linear recording density, perpendicular recording having an easy axis of magnetization in the perpendicular direction of a recording layer, and transverse recording having an easy axis of magnetization in a track direction within a film plane are available. These recording processes are expected to achieve an ever-higher recording density because demagnetization due to a demagnetizing field is more reduced than that in conventional longitudinal recording. Another proposal is made of a magnetic disk medium using a patterned medium comprising a substrate, a non-magnetic film such as an organic film or an Si film provided on the substrate, and unit minuscule recording areas obtained by embedding a magnetic thin film in recesses physically formed in the surface of the non-magnetic film. Never until now are a magnetic head used on the magnetic disk medium and how to record information thereon proposed.
A magnetic disk medium using such a patterned medium as mentioned above, for instance, a medium shown at
100
in
FIGS. 3 and 4
, comprises a disk form of substrate
102
, a multiplicity of unit minuscule recording areas
104
formed of a magnetic material on the substrate
102
to magnetically record information thereon and located concentrically or spirally at an interval in a peripheral or radial direction, and a non-recording area
106
formed of a non-magnetic material that is embedded between unit minuscule recording areas. In the medium shown in
FIG. 3
, each of the unit minuscule recording areas
104
is in a rectangular form having a major axis and a minor axis, with the major axis direction aligned with the peripheral direction of the substrate, and in the medium shown in
FIG. 4
, each of the unit minuscule recording areas
104
is in a substantially cuboidal form. In the magnetic disk medium having such unit minuscule recording areas, the unit minuscule recording areas are individually isolated by the non-magnetic material from one another, so that fringing between adjacent unit minuscule recording areas can be eliminated. In the structure shown in
FIG. 3
, however, the improvement in the transfer rate of data is not always satisfactory. For the structure shown in
FIG. 4
, on the other hand, some contrivance is needed because perpendicular magnetic recording is carried out with a recording magnetic pole; that is, it is required to provide a return path or soft magnetic under layer in the medium, thereby achieving recording magnetic field enhancement.
It is therefore an object of the invention to provide a magnetic disk medium and magnetic recording system, which use a patterned medium structure as mentioned above so that the high transfer rate of data can be achieved with no fringing problem.
SUMMARY OF THE INVENTION
The above object is achieved by the inventions defined below as (1) to (5).
(1) A magnetic disk medium comprising a disk form of substrate, a multiplicity of unit minuscule recording areas formed of a magnetic material on said substrate to magnetically record information thereon and located concentrically or spirally at an interval in a peripheral or radial direction, and a non-recording area provided on said substrate and formed of a non-magnetic material that is embedded between said unit minuscule recording areas, each of said unit minuscule recording areas being in a form having a major axis and a minor axis, wherein a direction of said major axis is aligned with a radial direction of said substrate.
(2) The magnetic disk medium according to (1), wherein each of said unit minuscule recording areas comprises a single domain structure with an easy axis of magnetization thereof aligned with the direction of said major axis.
(3) A magnetic recording system that is a magnetic disk system comprising a magnetic head for writing information on a magnetic disk medium as recited in (1) or (2) and/or reading information from said magnetic disk medium, wherein said magnetic head comprises an upper magnetic thin film and a lower magnetic thin film that form a magnetic circuit with a magnetic gap located therebetween and a conductive coil that intersects said magnetic circuit, with a direction of a magnetic gap line aligned with a peripheral direction of said magnetic disk medium.
(4) The magnetic recording system according to (3), wherein said magnetic head is a thin-film magnetic head in which thin films are formed and stacked one upon another in a widthwise direction of a magnetic pole so as to have a narrow magnetic pole width.
(5) The magnetic recording system according to (3) or (4), wherein a length of upper and lower magnetic poles formed by said upper magnetic thin film and said lower magnetic thin film in a radial direction of said medium is gradually diminished toward ends thereof that opposite to said medium.
ADVANTAGES OF THE INVENTION
According to the invention, fringing between adjacent unit minuscule recording areas is prevented by use of a patterned medium structure. In addition, each unit minuscule recording area is in a form having a major axis and a minor axis, wherein the direction of the major axis is aligned with the radial direction of the magnetic disk medium and the direction of the minor axis is aligned with the peripheral direction thereof, so that the magnetic disk medium can have an increased recording density in the peripheral direction. It is thus possible to achieve an ever-higher transfer rate of data.
By using a patterned medium having a single domain structure (with the easy axis of magnetization aligned with the major axis direction of each unit minuscule recording area, i.e., the radial direction of the medium) for the magnetic disk medium, it is possible to make the diameter of crystal grains therein larger than those in a medium having a continuous recording layer on one side of a disk (for instance, the medium disclosed in JP-A-9-97419), even when they have the same linear recording density. Thus, the deterioration of magnetization due to thermal fluctuation can be reduced or eliminated and the single domain structure can ensure to achieve an ever-higher switching rate of magnetization. In the above patterned medium structure, the higher the linear recording density, the more is the influence of the demagn
Aoyama Tsutomu
Hattori Kazuhiro
Sato Isamu
Cao Allen
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
TDK Corporation
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