JPH11283231A - Perpendicular magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form magnetic walls, to improve productivity and to reduce medium noise by forming the magnetic walls made of soft magnetic substrate layers at the periodic places with respect to the running direction of a head and making magnetic domains intermixed in a reversely parallel manner. SOLUTION: A film forming of the magnetic layers, which constitute the medium, is conducted on a substrate 4 by a magnetron sputtering method. During the film forming, an approximately 4 kA/m magnetic field is applied to the substrate 4 by the magnet of the magnetron in the radial direction of the substrate 4 and the magnetization of a hard magnetic pinning layer 6 and a soft magnetic substrate layer 8 and easily-magnetized axes are aligned in the radial direction. The layers 6 and 8 are alternatively coupled and the magnetization directions are directed toward the center of the medium 2 throughout the surface of the medium 2. Then, at three equally divided places in the peripheral direction of the medium 2, outwardly directed magnetic domains are formed by reversing the magnetization employing the permanent magnets whose magnetic pole surfaces are opposingly arranged at the outer peripheral surface of the medium 2. Thus, magnetic walls are formed at six boundary places between inwardly and outwardly directed magnetic domains looking to the peripheral direction. By mixing the reversely parallel magnetic domains, it is stabilized in a static magnetic manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a perpendicular magnetic recording medium having a perpendicular recording layer formed on a soft magnetic underlayer.

[0002]

2. Description of the Related Art Perpendicular magnetic recording has attracted attention because it allows higher-density recording than current longitudinal magnetic recording, and research and development are being conducted in various places.

By the way, in magnetic recording, especially in digital magnetic recording using a disk-shaped medium, various format signals such as an index signal, a sector identification signal and a servo signal are recorded on a medium surface before use. There is a need.

[0004] As a medium used for perpendicular magnetic recording,
Many studies have been made on a two-layer film medium comprising a soft magnetic underlayer and a perpendicular recording layer formed thereon. By using such a two-layer film medium in combination with a single pole type head, efficient recording and reproduction can be performed. Among them, Co-
A two-layer film medium having a Zr-based amorphous soft magnetic film as an underlayer can provide a perpendicular recording layer having a sharp perpendicular orientation, and is effective for a storage battery to improve recording efficiency (Japanese Patent Laid-Open No. 3-278).
No. 595).

[0005] The medium described in this document, particularly a disk-shaped medium, causes a problem that the signal intensity is attenuated with time only by rotating the medium after signal recording. This occurs because the magnetic field generated from the domain wall of the soft magnetic underlayer erases the recording signal of the perpendicular recording layer. The magnetic field generated from the domain wall of the soft magnetic underlayer also causes a problem of generating spike-shaped medium noise.

Accordingly, the present inventors have previously provided an in-plane oriented hard magnetic pinning layer having remanent magnetization in either the radially outward or inward direction between the substrate and the soft magnetic underlayer. Japanese Patent Laid-Open No. 7-129946 has previously proposed a technique for preventing demagnetization due to rotation of a medium without impairing recording / reproducing characteristics and reducing medium noise. According to this proposal, the in-plane oriented hard magnetic pinning layer is made of CoS
A particularly large effect can be obtained when the medium has a uniaxial magnetic anisotropy in the radial direction of the disk-shaped medium such as m.

On the other hand, in a current magnetic recording device, a format signal is recorded on a medium surface by a magnetic head.

[0008]

However, as described in Japanese Patent Application Laid-Open No. 7-129946, the state in which the underlayer has a remanent magnetization in either the outward or inward radial direction is a static state. Because it is magnetically unstable,
The direction of the remanent magnetization is slightly deviated from the radial direction, a reverse magnetic domain is easily generated in an unspecified location due to the influence of an external magnetic field or the like, and a spike-like noise is generated on the domain wall in that portion.

Also, the format signal has to be recorded over a wide usable area of the medium, and it takes too much time to record by a magnetic head as in the current magnetic recording apparatus. In particular, as the recording density increases,
The time required increases, leading to a decrease in productivity.
Further, writing a format signal using a magnetic head requires a large-scale servo writer, which leads to an increase in cost.

Accordingly, an object of the present invention is to provide a perpendicular magnetic recording medium capable of suppressing the generation of harmful noise on a data area and recording in a short time and at a low cost as compared with a method of recording with a magnetic head. I do.

[0011]

According to a first aspect of the present invention, there is provided a perpendicular magnetic recording medium in which a perpendicular recording layer is formed on a soft magnetic underlayer. A domain wall of the soft magnetic underlayer is formed at a periodic place, and antiparallel magnetic domains are mixed.

According to a second aspect of the present invention, in the perpendicular magnetic recording medium according to the first aspect, the perpendicular magnetic recording medium has a three-layer structure having a hard magnetic pinning layer for fixing a magnetic domain of the soft magnetic underlayer.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Summary of the Invention) In the present invention, the direction of the remanent magnetization of a soft magnetic underlayer is changed to the right or left with respect to the running direction of a head in accordance with the location of a medium surface. A domain wall is formed in advance in a suitable location, and this is used as a format signal or a part thereof. If antiparallel magnetic domains coexist in this way, it is magnetostatically stable and the generation of harmful domain walls on the data area can be suppressed. Note that the rightward and leftward controls can be easily performed using, for example, a permanent magnet or an electromagnet, and the productivity can be improved. Furthermore, the cost can be reduced without requiring a large-scale device such as a servo writer for writing the format signal.

(Embodiment 1) An embodiment in which each magnetic layer of a medium is formed using a magnetron sputtering method will be described. Perpendicular magnetic recording medium 2 shown in FIG.
Describes that a Co-Sm hard magnetic pinning layer 6 is formed on a 3.5-inch disk-shaped mirror-polished glass substrate 4 by 150 mm.
nm, the Co-Zr-Nb soft magnetic underlayer 8 is 500 nm,
Further, a 50 nm thick Co-Cr-Ta perpendicular recording layer 10 and a protective layer 12 are sequentially formed, and substantially a hard magnetic pinning layer 6, a soft magnetic underlayer 8, and a perpendicular recording layer 10 are formed.
This constitutes a perpendicular magnetic recording medium 2 having a layer structure. The hard magnetic pinning layer 6 is provided for fixing the magnetic domain of the soft magnetic underlayer 8.

During the film formation, a magnetic field of about 4 kA / m is applied in the radial direction of the substrate 4 by a magnetron magnet, and the magnetization and the easy axis of magnetization of the hard magnetic pinning layer 6 and the soft magnetic underlayer 8 are aligned in the radial direction. The hard magnetic pinning layer 6 and the soft magnetic underlayer 8 are exchange-coupled, and the magnetization of the Co—Sm hard magnetic pinning layer 6 and the Co—Zr—Nb soft magnetic underlayer 8 extends over the entire surface of the medium 2. The direction is toward the center of the medium 2. The method of turning the magnetization directions of the hard magnetic pinning layer 6 and the soft magnetic underlayer 8 toward the center includes:
In addition to the above, it is also possible to use a permanent magnet or the like after film formation.

Next, as shown in FIG. 1, permanent magnets whose magnetic pole faces are opposed to the outer peripheral surface of the medium 2 at three equally spaced positions in the circumferential direction of the medium 2 which originally form the inward magnetic domains 14. Is used to reverse the magnetization to form outward magnetic domains 16. As a result, domain walls 18 are formed at six boundaries between the inward magnetic domains 14 and the outward magnetic domains 16 as viewed in the circumferential direction. No writing is performed on the medium 2 by the head.

Next, using a magnetoresistive head (MR head) having a track width of 2.6 μm, a medium rotation speed of 2260 r.
At pm, the written medium was reproduced. FIG. 3 shows the envelope of the reproduction voltage from the head for one rotation of the medium at this time. A clear output pulse is observed depending on the location of the domain wall 18 formed on the medium 2, which indicates that the output pulse can be sufficiently used as a format signal. In addition, since the output pulse is observed at the same place as in FIG. 3 over the entire surface of the medium 2, the magnetic domain structure of the Co—Sm hard magnetic pinning layer 6 and the Co—Zr—Nb soft magnetic underlayer 8 is changed as shown in FIG.
You can see that it looks like This is because the axes of easy magnetization of the hard magnetic pinning layer 6 and the soft magnetic underlayer 8 are aligned in the radial direction and are exchange-coupled, so that even the magnetic field having a large distribution such as a permanent magnet can be easily ordered.
8 can be formed.

Comparative Example Next, a comparative example will be described. With respect to the same perpendicular magnetic recording medium 2 used in the first embodiment, the magnetization of the Co-Sm hard magnetic pinning layer 6 and the Co-Zr-Nb soft magnetic underlayer 8 is set to 100 kA / m or more by a permanent magnet over the entire surface. Reproduction was performed under the same conditions as in the embodiment, with the strong radial magnetic field applied. FIG. 4 shows the envelope of the reproduction voltage from the head for one rotation of the medium at this time. In this case, occurrence of irregular noise pulses is observed at several places. From the analysis of the noise pulse, as shown in FIG.
In the above, the Co-Sm hard magnetic pinning layer 6 and the Co-Zr
As shown in the drawing, the magnetization direction of the -Nb soft magnetic underlayer 8 and the domain wall 22 are irregularly formed in order to alleviate magnetostatic instability as shown in FIG. That is the cause.

(Embodiment 2) In the above-described embodiment, only the disk-shaped recording medium 2 has been described. However, the present invention can be applied to a tape-shaped recording medium as long as a control signal is input in advance. This is because there is only a difference between the running direction in the circumferential direction and the straight longitudinal direction. This will be described with reference to FIG. FIG. 6 is a plan view of a perpendicular magnetic recording medium 30 made of a long tape, which has an easy axis 32 in the width direction and a hard axis 34 in a running direction perpendicular to the width direction. By causing the recording medium 30 to travel in the longitudinal direction at a predetermined traveling speed and applying an alternating magnetic field in the width direction by the electromagnet 42 in synchronization with the traveling speed, the magnetic domains 36 and the magnetic domains 38 that are in an inverting relationship are alternately formed. Thus, the domain wall 40 is formed at the boundary between the magnetic domains 36 and 38, and the same operation and effect as described in the first embodiment can be obtained.

[0020]

According to the present invention, since no magnetic field is formed in the data area, the medium noise is small and the error rate is small. Further, since a servo writer is not required, the cost is low, and the domain wall can be formed using a permanent magnet or an electromagnet, so that productivity is high.

[Brief description of the drawings]

FIG. 1 is a plan view for explaining magnetic domains and domain walls of a perpendicular magnetic recording medium according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a perpendicular magnetic recording medium according to the present invention.

FIG. 3 is a characteristic diagram showing a head output for one rotation of a perpendicular magnetic recording medium according to an embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a head output for one rotation of a perpendicular magnetic recording medium according to a comparative example.

FIG. 5 is a plan view for explaining magnetic domains and domain walls of a perpendicular magnetic recording medium according to a comparative example.

FIG. 6 is a plan view for explaining magnetic domains and domain walls of a perpendicular magnetic recording medium according to another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 2 perpendicular magnetic recording medium 4 glass substrate 6 hard magnetic pinning layer 8 soft magnetic underlayer 10 perpendicular recording layer 12 protective layer 14 inward magnetic domain 16 outward magnetic domain 18 domain wall 30 perpendicular magnetic recording medium 32 easy axis of magnetization 34 hard axis of magnetization 36, 38 magnetic domains 40 domain walls

Claims (2)

[Claims] In a perpendicular magnetic recording medium in which a perpendicular recording layer is formed on a soft magnetic underlayer, a domain wall of the soft magnetic underlayer is formed at a location that is periodic with respect to a running direction of a head, and an antiparallel magnetic wall is formed. A perpendicular magnetic recording medium characterized by a mixture of magnetic domains. 2. The perpendicular magnetic recording medium according to claim 1, wherein the medium has a three-layer structure including a hard magnetic pinning layer for fixing a magnetic domain of the soft magnetic underlayer.