The present invention relates to recording heads for use with magnetic storage media, and more particularly relates to a perpendicular recording head which generates a background magnetic field in the magnetic media.
Perpendicular magnetic recording heads have been developed for use in hard disk drive systems. Some examples of perpendicular recording heads are described in U.S. Pat. No. 4,438,471 to Ashiki et al., U.S. Pat. No. 4,541,026 to Bonin et al., U.S. Pat. No. 4,546,398 to Toda et al., U.S. Pat. No. 4,575,777 to Hosokawa, U.S. Pat. No. 4,613,918 to Kanai et al., U.S. Pat. No. 4,649,449 to Sawada et al., U.S. Pat. No. 4,731,157 to Lazzari, U.S. Pat. No. 4,974,110 to Kanamine et al., and U.S. Pat. No. 5,738,927 to Nakamura et al.
In order to increase the data storage density of hard disk drives, the use of magnetic media having increased magnetic anisotropy has been proposed. However, highly anisotropic media exhibit extremely high coercivities, e.g., well over 5,000 Oe. Conventional perpendicular magnetic recording heads are not capable of recording on media having such high coercivities.
The present invention has been developed in view of the foregoing, and to address other deficiencies of the prior art.
The present invention provides a magnetic recording head for use with magnetic recording media having a magnetic field generating coil configured and positioned to generate a background magnetic field in the magnetic recording media.
The magnetic recording head preferably comprises a perpendicular configuration. In accordance with the present invention, the perpendicular recording head generates a supplemental magnetic field which increases the magnetic recording field in comparison with conventional perpendicular recording heads. Although not limited to such use, perpendicular recording heads of the present invention are particularly useful for computer hard disk drives.
A typical perpendicular recording head includes a main pole, an opposing pole magnetically coupled to the main pole, and an electrically conductive magnetizing coil surrounding the main pole. The bottom of the opposing pole will typically have a surface area greatly exceeding the surface area of the tip of the main pole. In a preferred embodiment, electrical current flowing through the magnetizing coil creates a flux through the main pole tip and also generates the background magnetic field in the recording media.
A typical magnetic recording medium for use in conjunction with the present perpendicular recording head includes an upper layer having multiple magnetically permeable tracks separated by nonmagnetic transitions, and a magnetically permeable lower level. The lower level is magnetically soft relative to the tracks.
To write to the magnetic recording medium, the recording head is separated from the magnetic recording medium by a distance known as the flying height. The magnetic recording medium is moved past the recording head so that the recording head follows the tracks of the magnetic recording medium, with the magnetic recording medium first passing under the opposing pole and then passing under the main pole. Current is passed through the coil to create magnetic flux within the main pole. The magnetic flux will pass from the main pole tip through the track, into the lower layer, and across to the opposing pole. In addition to the magnetic field generated at the main pole tip, a supplemental magnetic field is generated in accordance with the present invention. The combined magnetic flux from the pole tip and from the coil causes the magnetic fields in the tracks to align with the magnetic flux of the recording head. Changing the direction of electric current changes the direction of the flux created by the recording head and therefore the magnetic fields within the magnetic recording medium.
An aspect of the present invention is to provide a perpendicular recording head including a main pole having a tip, and an electrically conductive magnetizing coil positioned sufficiently close the main pole tip to generate a background magnetic field in the magnetic recording medium when current is passed through the magnetizing coil.
Another aspect of the present invention is to provide a magnetic recording apparatus comprising a magnetic recording medium and a recording head. The magnetic recording medium includes an upper layer having a plurality of data storage tracks, and a lower layer being magnetically soft relative to the data storage tracks. The recording head includes a main pole having a tip, and an electrically conductive magnetizing coil positioned sufficiently close the main pole tip to generate a background magnetic field in the magnetic recording medium when the recording head is positioned at a flying height above the magnetic recording medium and current is passed through the magnetizing coil.
A further aspect of the present invention is to provide a method of storing data on a magnetic storage medium. The method includes the steps of providing a magnetically permeable main pole, providing a magnetic storage medium adjacent the main pole, directing magnetic flux from the main pole toward the magnetic storage medium, and additionally generating a background magnetic field in the magnetic storage medium.
These and other aspects of the present invention will be more apparent from the following description.
The preferred embodiment of the present invention provides a perpendicular recording head for use with magnetic recording media. As used herein, “recording head” means a head adapted for read and/or write operations.
The present invention has been developed in order to overcome certain problems with conventional hard disk drive systems. Granular magnetic recording media used in such systems is subject to superparamagnetic instabilities when the anisotropy energy of the grains (Ku×V, where V is the grain volume) becomes comparable to the energy of thermal fluctuations, kT. Improvements in recording densities requires continuous refinement of the grain size. Higher anisotropy materials are desirable in order to keep the media thermally stable. As an example, the L10 phase of Co50Pt50 has an anisotropy energy Ku=4×106 J/m3 (compare with Ku=˜105 J/m3 for CoCr media). Such high anisotropy reduces the critical size at which grains become thermally unstable to less than 1 nm. Utilizing these materials for recording media can potentially extend the recording densities well beyond 100 Gbit/in2. However, a major obstacle preventing utilization of high anisotropy media is that such media exhibit exceptionally high coercivities, e.g., in excess of 5,000 Oe.
The magnitude of the fields generated by conventional perpendicular recording heads is limited by the saturation moment of the yoke material.
As shown in
The recording layer 30 may be made of any suitable hard magnetic material such as CoCrPt, CoCrPtTa, CoCrPtB, CoCrPtTaNb or other high anisotropy hexagonal Co-containing alloys. The recording layer 30 may also be made of CoPt, FePt, CoPd, FePd or other high anisotropy L10 materials. High anisotropy materials such as Co/Pd, CoB/Pd, CoCr/Pd, CoCrPt/Pd, CoCrPd/Pt, CoB/Pt, Co/Pt, CoCr/Pt, Fe/Pd and Fe/Pt may also be used as the recording layer 30. Furthermore, high anisotropy ferrites such as Ba ferrite may be used as the recording layer 30. Preferred materials for the recording layer 30 include L10 materials such as CoPt, FePt, CoPd and FePd, and multilayers of Co/Pt and Co/Pd. The recording layer may have a relatively high anisotropy energy Ku, e.g., greater than about 106 J/m3. For example, recording layers having anisotropy energy Ku levels of from about 106 to about 108 μm3 may be used. The recording layer may also have a relatively high coercivity above 5,000 Oe, e.g., above 8,000 or 10,000 Oe. The underlayer 32 may be made of any suitable soft magnetic material, such as FeAlN, FeTaN, CoFe, CoFeB, CoFeN or other high moment soft magnetic materials or soft magnetic films comprising multiple layers of such materials.
The dimensions R, D, H, Z, Ty and Tp are preferably selected in accordance with the present invention to produce a sufficient background magnetic field in the recording layer 30 when current flows through the coil 20. For many perpendicular recording head configurations, R preferably ranges from about 0.1 to about 5 micron, D ranges from about 0.1 to about 5 micron, H ranges from zero to about 0.1 micron, and Z ranges from about 0.1 to about 5 micron. The yoke thickness Ty may typically be from about 0.1 to about 5 micron, preferably from about 0.1 to about 1 micron. The main pole thickness Tp may be from about 0.01 to about 0.5 micron, preferably from about 0.01 to about 0.1 micron.
In accordance with the present invention, the ratio of the coil radial dimension R to the distance D is preferably controlled in order to generate the desired background magnetic field in the recording layer 30, as more fully described below. The ratio of R:D typically ranges from about 1:1 to about 10:1, preferably from about 1:1 to about 5:1. The ratio of the yoke thickness Ty to the pole thickness Tp is also controlled. The ratio of Ty:Tp preferably ranges from about 1:1 to about 10:1. More preferably, the ratio of Ty:Tp ranges from about 2:1 to about 5:1.
Although the magnetizing coil 20 shown in
In the embodiments shown in
In accordance with the present invention, the amount of electrical current supplied to the magnetizing coil 20 is controlled in order to generate the desired background magnetic field strength at the recording layer 30, the background magnetic field is typically greater than 100 Gauss, preferably greater than 1,000 or 2,000 Gauss. Depending upon the magnetic properties of the recording layer 30, the background magnetic field may typically range from about 100 to about 20,000 Gauss, preferably from about 1,000 to about 15,000 Gauss, and more preferably from about 5,000 to about 10,000 Gauss at the recording layer 30. The background magnetic field effectively decreases the coercivity of the recording layer 30. The coercivity of the recording layer 30 may be defined as Hc, and the background magnetic field effectively decreases the coercivity Hc to a lower value defined as Hb. The ratio of Hb:Hc preferably ranges from about 1:10 to about 9:10, more preferably from about 3:10 to about 8:10. In a particularly preferred embodiment, the ratio of Hb:Hc is about 5:10.
In accordance with a further aspect of the present invention, the level of the background magnetic field Hb is controlled in relation to the strength of the magnetic field Hp generated at the main pole tip 16. Preferably, the ratio of Hb:Hp is from about 1:10 to about 10:1, more preferably from about 4:10 to about 3:1. As a particular example, a recording layer having a coercivity of 10,000 Oe may be written on with a recording head of the present invention which generates a pole tip coercivity Hp of 5,000 Oe and a background coercivity Hb of 8,000 Oe. Thus, while the magnetic flux generated from the pole tip would not be sufficient to write on the recording layer alone, the background magnetic field is sufficient to effectively reduce the dynamic coercivity of the recording layer, thereby enabling writing on the recording layer.
As long as the pole tip is not completely saturated, the magnetic flux is mainly concentrated within the pole tip. A standard way of operating a single pole head is to choose a current value SAT that causes complete saturation of the pole tip. The fields generated by the saturated pole are localized and their gradients within the recording layer determine the minimum bit cell size. If the current in the coil is further increased by ΔI (ΔI=I-ISAT), the extra flux generated will no longer be confined to the pole tip. The magnitude of the additional field AB will be proportional to ΔI. The field flux will be spread over a significantly larger region within the recording layer, the size of which is determined by the diameter of the coil due to the relative proximity of the coil to the recording layer. The magnitude of ΔB can be fine-tuned by the current in the coil. For a single turn coil the magnitude of ΔB is given by:
where R is the radius of the coil and z is the distance from the coil to the hard layer. For R=0.2 μm and z=0.1 μm, background fields in excess of 1Tesla (10,000 Oe) can be generated with currents as small as 400 mA with a resolution of about 25 Oe/mA if a single turn coil is used.
The presence of the additional background field AB effectively reduces coercivity of the recording layer. It enables writing on high coercivity media using heads based on available soft materials. Because of high data rates, the dynamic coercivity will be affected by the introduction of such background field because the dynamic coercivity is significantly higher than the static coercivity.
A test was conducted to confirm the performance of the present design.
The present recording system effectively reduces the coercivity of the media. This is accomplished by generating a background field utilizing a magnetizing coil which is placed in proximity to the recording layer. This recording system enables writing on high coercivity/high anisotropy media that can support very high recording densities, e.g., in excess of 100 Gbit/in2. High recording densities can therefore be achieved without the necessity of major changes in the recording process.
Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.
This application is a National Stage (371) appl. of PCT/US00/25650, filed Sep. 9, 2000, which claims the benefit of U.S. Provisional Patent Application No. 60/154,880, filed Sep. 20, 1999.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCTUS00/25650 | 9/19/2000 | WO | 00 | 2/8/2002 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO0122407 | 3/29/2001 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4138702 | Magnenet | Feb 1979 | A |
4438471 | Oshiki et al. | Mar 1984 | A |
4541026 | Bonin et al. | Sep 1985 | A |
4546398 | Toda et al. | Oct 1985 | A |
4575777 | Hosokawa | Mar 1986 | A |
4613918 | Kanai et al. | Sep 1986 | A |
4649449 | Sawada et al. | Mar 1987 | A |
4652956 | Schewe | Mar 1987 | A |
4731157 | Lazzari | Mar 1988 | A |
4742413 | Schewe | May 1988 | A |
4943882 | Wada et al. | Jul 1990 | A |
4974110 | Kanamine et al. | Nov 1990 | A |
5073836 | Gill et al. | Dec 1991 | A |
RE33949 | Mallary et al. | Jun 1992 | E |
5225953 | Wada et al. | Jul 1993 | A |
5687046 | Mathews | Nov 1997 | A |
5738927 | Nakamura et al. | Apr 1998 | A |
Number | Date | Country |
---|---|---|
0 326 904 | Aug 1989 | EP |
0362904 | Aug 1989 | EP |
54128719 | May 1979 | JP |
54128719 | Oct 1979 | JP |
55055420 | Apr 1980 | JP |
55080818 | Jun 1980 | JP |
56087218 | Jul 1981 | JP |
57033421 | Feb 1982 | JP |
59195311 | Nov 1984 | JP |
59231720 | Dec 1984 | JP |
60059515 | Apr 1985 | JP |
60124014 | Jul 1985 | JP |
07105501 | Apr 1995 | JP |
Number | Date | Country | |
---|---|---|---|
60154880 | Sep 1999 | US |