Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
1999-08-19
2001-07-24
Ometz, David L. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S135000
Reexamination Certificate
active
06266210
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic disc device used in computers, information storage devices and so on, a magnetic storage device used in such information home appliances as digital VTRs, and a magnetic recording, and and, more particularly, to a magnetic recording and reading device suitable for realizing high-speed recording and reading, and for high-density recording.
Semiconductor memories, magnetic memories, etc., are used in the storage or recording devices of information equipment. Semiconductor memories are used in internal primary storage in the light of high-speed accessibility and magnetic memories are used in external secondary storages in the light of a high capacity, low cost and nonvolatile property. Magnetic disk devices, magnetic tapes and magnetic cards are the main current in magnetic memories. A magnetic recording portion which produces a strong magnetic field is used in order for writing magnetic information in recording media, such as magnetic disks, magnetic tapes or magnetic cards. Further, reading portions based on the magnetoresistance effect or the electromagnetic induction effect are used in reading magnetic information recorded at a high desisty. In recent years, for reading, the giant magnetoresistance effect and the tunneling magnetoresistive effect have also begun to be examined. These functional portions for recording and reading are both installed in an input-output part which is called a magnetic head.
The basic configuration of a magnetic disk device is shown in
FIGS. 10A and 10B
.
FIG. 10A
shows a plan view of the device and
FIG. 10B
shows a vertical-sectional view of the device. Recording media
101
-
1
to
101
-
4
are fixed to a hub
104
to be rotated by a motor
100
. In
FIG. 10B
shows one example which comprises four magnetic disks
101
-
1
to
101
-
4
and eight magnetic heads
102
-
1
to
102
-
8
. However, the magnetic disk device may comprise at least one magnetic disk and at least one magnetic head. The magnetic heads
102
-
1
to
102
-
8
move on the rotating recording media. The magnetic heads
102
-
1
to
102
-
8
are supported by a rotary actuator
103
via arms
105
-
1
to
105
-
8
. Suspensions
106
-
1
to
106
-
8
have function of a the pressing the magnetic heads
102
against the recording media
101
-
1
to
101
-
4
under a determined load, respectively. A given electric circuit is needed for processing of reproduction signals and for inputting and outputting of information. Recently, a signal processing circuit in which waveform interference at high-density is positively utilized, such as PRML (Partial Response Maximum Likelihood) or EPRML (Extended PRML) which is an enhanced PRML, has been adopted, contributing greatly to a high-density design. The signal processing circuit is installed in a circuit board on a cover
108
, etc.
The functional portion for writing and reading information on a magnetic head assembly is comprises components shown in
FIG. 11A
, for example. A writing portion
111
is comprised of a spiral coil
116
between magnetic poles
117
,
118
which are magnetically connected with each other. The magnetic poles
117
,
118
are both composed of a magnetic film pattern, which are made of an NiFe alloy, etc., respectively. The reading portion
112
comprises a magnetoresistance element
113
made of an NiFe alloy, etc. and an electrode
119
for applying a constant current or a constant voltage to the element
113
and for detecting changes in resistance. The magnetic pole
118
, which is made of an NiFe alloy, etc. and serves also as a magnetic shielding layer, is provided between the writing and reading portions. There is further a shielding layer
115
underneath the magnetoresistance element
113
. A reading resolution is determined by the clearance distance between the shielding layer
115
and the magnetic pole
118
(serving also as another shielding layer). The functional portion is formed on a magnetic head slider
1110
(
FIG. 11B
) via an underlayer
114
made of Al
2
O
3
, etc. Incidentally, the magnetic head slider, which is provided with a protection layer made of hard-carbon, etc. on the surface opposed to the magnetic recording medium, is supported by a gimbal
1111
and a suspension
1113
, as shown in FIG.
11
B. The magnetic head slider moves relatively to the magnetic recording medium while floating from the medium surface and, after positioning in an arbitrary position by an arm
1114
connected to a motor, realizes the function of writing or reading magnetic information via lead lines
1116
and
1115
. With respect to the above function, there is also provided an electric control circuit together with the aforementioned signal processing unit or on the head carriage.
A detailed structure of a recording medium is schematically shown in FIG.
12
. As described in JP-A-3-16013, most of the conventionally used recording media are produced by forming a magnetic layer
123
made of a Co—Cr—Ta alloy, or a Co—Cr—Pt alloy, etc. on a non-magnetic substrate made of Al plated with an NiP alloy, a glass, a high-hardness ceramics, a polished Si or the like, or a plastic substrate
121
by the sputtering method, or the evaporation method, or the plating method, etc. Usually, an under layer
122
made of Cr, or a Cr alloy, etc. for orientation control of the magnetic layer is often formed on the substrate. Furthermore, a protection film
124
made of diamond-like carbon containing nitrogen and/or hydrogen, or SiO
2
or SiN or ZrO
2
, etc. is provided to ensure durability of sliding resistance, and a lubricating film
125
made of perfluoro alkyl polyether having an adsorptive or a reactive end group, or organic fatty acids, etc. is provided.
In addition to the magnetic recording device, magneto-optic recording devices that perform recording and reading on a magnetic recording medium through the use of light have also been put to practical use. The magneto-optic recording devices are classified into one type in which recording is performed only by light modulation and another type in which recording and reproduction are performed by light with a modulated magnetic field. However, the both types greatly rely on heat when recording and reading. Therefore, according to such type of devices, it is impossible to perform recording and reading in high data transfer rate and thus they have been adopted mainly in backup systems, etc.
The importance of a storage device is determined by its storage capacity and the speed during inputting-outputting operations. In order to increase competitiveness of products, it is necessary for the storage device to increase capacity by higher recording density, higher rotational speed and higher data transfer rate than those of the prior art. Thus, an important problem to be solved by the present invention is to provide a device capable of recording and reading at a high data transfer rate of not less than 50 MB/s and, more preferably, that at a high density of not less than 5 Gb/in
2
. A magnetic recording medium capable of recording and reading at a high frequency and capable of obtaining a high S/N ratio at a high density and a magnetic head capable of generating a sufficient magnetic recording field at a high frequency are necessary for meeting the requirement.
In conventional magnetic recording media, there have been proposed and actually carried out to reduce noise by refining crystal grains in order to obtain a high S/N ratio at a high density of about 1 to 3 Gb/in
2
, and by promoting segregation of non-magnetic components at grain boundaries to reduce exchange coupling among crystal grains as being taught in JP-A-63-148411, JP-A-3-16013 and JP-A-63-234407 so as to make the coercive squareness S* to not more than 0.85 and the rotational hysteresis loss RH to the range of 0.4 to 1.3. Noise can be considerably reduced by recording and reading at a data transfer rate of not more than about 20 MB/s. However, when the magnetic recording was carried out on that film media of the prior art at a high frequency of n
Altman, III Franklin D.
Antonelli Terry Stout & Kraus LLP
Hitachi Ltd
Ometz David L.
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