JP2000222846A - Magnetic recording medium, recording method, and magnetic recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic recording medium, a recording method, and a magnetic recording device that have the large reproduction output and S/N of a servo signal, can accurately carry out tracking, and can reduce a track pitch for performing high-density recording. SOLUTION: A magnetic recording medium has a substrate 10 and a magnetic layer 11 on the substrate 10. In the servo signal recording region of the substrate 10, a projection part 12 is provided. A servo signal is recorded to the magnetic layer 11 on the projection part 12. The servo signal is recorded to the magnetic layer on one projection part 12 so that a magnetization direction is inverted for three times. To write the servo signal, one circuit of the desired number of clock signals is written at fixed intervals at an outermost periphery part on a disk. The signal is read by a clock head for synchronizing, and a high-frequency signal being synchronized with the signal is used for writing by a magnetic head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic disk, a recording method, and a magnetic recording apparatus, and more particularly to a servo signal recording portion having a convex portion and a concave portion. The present invention relates to a magnetic recording medium on which a signal is recorded, a method of recording the servo signal, and a magnetic recording device provided with the magnetic recording medium.

[0002]

2. Description of the Related Art In a magnetic disk such as a hard disk, a servo signal recording unit is provided for servoing a recording track. This servo signal recording portion is constituted by a concave portion and a convex portion, and a servo signal is recorded on a magnetic layer on the convex portion (for example, US Pat. No. 4,912,585;
JP-A-5-242470).

FIGS. 3 to 5 are explanatory views of a magnetic recording medium according to an embodiment of the invention of Japanese Patent Laid-Open No. 5-242470, and FIG. 6 is an explanatory view of a magnetic recording medium showing a comparative example with respect to the invention of the same publication.

[0004] This publication relates to a discrete track medium in which grooves 4 are formed in the circumferential direction between recording tracks 3. 3 and 4, reference numeral 1 denotes a substrate, and 2 denotes a magnetic layer. A servo signal recording portion is formed by forming a groove 6 that traverses the track 3 in the radial direction of the substrate 1. The direction of magnetization (magnetization direction) of the convex portion of the servo signal recording section in FIG. 5 is opposite to the direction of magnetization of the groove 6 (concave portion). By reversing the magnetization direction between the convex portion and the concave portion as shown in FIG. 5, the magnetization direction is inverted between the rising portion and the falling portion of the convex portion. However, as compared with a magnetic recording medium in which a servo signal is recorded only on a convex portion as shown in FIG. 6 (corresponding to U.S. Pat. No. 4,912,585).

In Japanese Unexamined Patent Application Publication No. 5-242470, after the convex and concave portions are simultaneously DC-magnetized in one direction, the write current is changed, and only the convex portions are DC-magnetized in the opposite direction. The directions are reversed.

[0006]

As shown in FIG. 6, in the case of the servo signal recording method in which only the convex portions are magnetized, the concave portions are not magnetized, so that there is no boundary region in which the magnetization direction is completely reversed, and thus, there is a problem. Signal is small and the S / N ratio is low. Therefore, when the output of the medium is reduced due to the narrow track width due to the high density, there is a problem that a good signal cannot be obtained.

In the case of the servo signal recording method in which the protrusions and the recesses are magnetized in opposite directions, as in the invention of Japanese Patent Application Laid-Open No. 5-242470 shown in FIGS.
Although a large signal can be obtained, the magnetization reversal region can be formed only at the uneven boundary. Further, with respect to the uneven pattern of the disk substrate, it is not possible to form a pattern as fine as the switching interval obtained when magnetic recording is performed due to processing restrictions.
For these reasons, there is a problem that the frequency of the obtained signal is low, and it is also weak against noise.

Further, in the servo signal recording method of the invention of the same publication, DC magnetization is used, and when writing a servo signal to a convex portion, the condition is such that only the convex portion is magnetized without magnetizing the concave portion. There is also a problem that the design greatly depends on the relationship between the current depth and the current depth.

The present invention relates to the reproduction output of servo signals and S / N
It is an object of the present invention to provide a magnetic recording medium, a recording method, and a magnetic recording apparatus that can perform high-accuracy recording by reducing the track pitch, which enables high-accuracy tracking.

[0010]

According to the magnetic recording medium of the present invention, a servo signal recording portion of a recording track is constituted by a concave portion and a convex portion. In a magnetic recording medium recorded so as to have a direction, the servo signal is recorded so that the magnetization direction is reversed at least once in a magnetic layer on one convex portion. .

In the magnetic recording medium of the present invention,
Since the servo signal written in the magnetic layer on the convex portion has a reversal portion of the magnetization direction, the reproduction output of the servo signal and the S / N
Is big. Moreover, in the present invention, it is sufficient to write the servo signal only on the magnetic layer on the convex portion, and it is not necessary to consider the influence on the magnetic layer on the concave portion when writing the servo signal. Therefore, when writing a servo signal to the magnetic layer on the convex portion, the write current can be selected so that a large magnetizing force acts on the magnetic layer, which also enables reproduction output and S / N
And signal quality can be improved. As a result, tracking accuracy is significantly improved.

It is sufficient that the magnetization direction is inverted at least once in one projection, but it is preferable that the magnetization direction is inverted two or more times, particularly three or more times, for example, three to five times.

In the present invention, the writing of the servo signal is performed by a magnetic head, and the direction of the magnetic flux generated from the magnetic head is reversed at least once while the magnetic head traverses one convex portion in the track direction. By using a high-frequency signal current as the servo signal writing current to the magnetic head, a servo signal recording method in which the magnetization direction of the convex portion is reversed can be achieved.

Preferably, the servo signal recording is performed before the magnetic recording medium is incorporated into the magnetic recording device, and thereafter, the magnetic recording medium is assembled into the magnetic recording device. In this way, servo signal recording can be performed by a dedicated device, servo recording can be performed with a head different from the data recording head of the drive, and the servo pattern design can be expanded or the timing for writing can be increased. There is room for selecting a means for obtaining a clock signal from various means such as a high-precision encoder.

Further, by using a high-frequency signal for recording the servo signal, unlike the DC magnetization, there is almost no dependence on the depth of the unevenness and the write current value, and only the convex portion can be selectively magnetized, and the design range is widened and the quality is stable. This brings the benefits mentioned above.

The magnetic recording apparatus of the present invention provides a magnetic recording medium of the present invention, a magnetic head, and a direction in which the magnetic head crosses a recording track (a direction including a radial direction of a disk).
Means for moving to

[0017]

FIG. 1 is a schematic perspective cross-sectional view showing a configuration near a servo signal recording portion of a magnetic recording medium according to an embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. It is a reproduction signal waveform diagram. In FIG. 2A, the thickness of the substrate and the magnetic layer
The heights and the like of the protrusions are schematically shown.

This magnetic recording medium has a magnetic layer 11 and other thin film layers on a substrate 10. This magnetic recording medium is provided with a data area having a track 16 for recording data, a recording area for an address code, a recording area for a clock signal, and a recording area for a servo signal, in the same manner as a normal magnetic recording medium. ing. A protrusion 12 is provided in the servo signal recording area of the substrate 10, and the servo signal is recorded on the magnetic layer 11 on the protrusion 12.

In this embodiment, as shown in FIG. 2A, a servo signal is recorded on the magnetic layer on one projection 12 so that the magnetization direction is reversed three times. In other words, the magnetic domains of the remanent magnetization are arranged three times in total on one convex portion 12 so that the magnetic domains of the remanent magnetization are the same as or opposite to the running direction (in the prior art examples shown in FIGS. The direction of the magnetic domain on the projection is the same as or opposite to the running direction, and there is no reversal).

When the servo signal recording section and the magnetic head move relative to each other in the track longitudinal direction by rotating the substrate 1, a remarkably large reproduction output is obtained in the three magnetization direction reversal portions as shown in FIG. 2B. / N also increases. Note that a reproduced signal is also generated at the rising portion and the falling portion of the convex portion 12, but this wave height is smaller than the output wave height of the magnetization direction reversing portion.

In order to write the servo signal, for example, a clock head writes a desired number of clock signals at a constant interval on the outermost peripheral portion of the disk for one round. This signal is read and synchronized by a clock head, and a servo signal is written to the convex portion by a magnetic head using a high-frequency signal synchronized with the clock. When performing this writing, it is preferable to use a write-only device. While rotating the substrate 10, a high-frequency signal is applied to the magnetic head of the write-only device to write a servo signal to the magnetic layer 11 on the convex portion 12. At this time, the frequency of the write high-frequency current according to the rotation speed of the substrate is set so that the alternating current of three cycles is supplied to the magnetic head while the magnetic head traverses one convex portion 12 in the left-right direction in FIG. By selecting, it is possible to obtain a servo signal recording whose magnetization direction is inverted three times as shown in FIG.

This servo signal is applied to the magnetic layer 11 on the convex portion 12.
However, the data is also written in other areas such as a data recording track, and the protrusion 12
Other servo signal records may be deleted.

When this servo signal is written in the convex portion 12, a slight magnetization is also generated in the magnetic layer 11 in the concave portion 15, but high-frequency magnetic recording is performed only in a portion where the distance between the head and the magnetic recording layer is short. It is performed strongly, and the residual magnetic flux decreases rapidly as the distance increases. For this reason, recording is hardly performed in the concave portion irrespective of its depth.
Servo signals are written only on the upper magnetic layer, and sharp recording and reproduction can be performed.

In the above embodiment, one projection 12
The magnetization direction is reversed three times in the magnetic layer 11 of
It may be one that is inverted only once as shown in FIG.
Other inversion numbers such as times may be used. However, in order to perform high-accuracy tracking, the number of inversions is preferably two or more, especially three or more. 3 to 5 practically
Preferably, the number of times.

In the above embodiment, recording track 1
Although no groove is provided between the six, the present invention can be applied to a discrete type magnetic recording medium provided with the groove 4 as shown in FIG.

The width of the protrusion 12 in the longitudinal direction of the track may be arbitrarily set, but is usually about 1 to 5 μm, and the height of the protrusion 12 is preferably about 100 to 300 nm. The interval between the convex portions in the track longitudinal direction is determined by the servo pattern, and may be set to an optimal value as appropriate. Usually, the interval between the convex portions 12 in the track longitudinal direction is generally the same as the interval between the convex portions in the track longitudinal direction. If the width of is set to 1, it is preferably about 0.5 to 2.

Preferred embodiments of the magnetic recording medium of the present invention, such as a substrate and a thin film, will be described below.

As the substrate of the magnetic recording medium of the present invention,
In addition to an Al alloy substrate such as an Al-Mg alloy containing l as a main component, ordinary soda glass, soda lime glass,
Glasses such as aluminosilicate glass, borosilicate glass, crystallized glass, metals and alloys such as silicon and titanium,
Any non-magnetic substrate such as a substrate made of ceramics and various resins can be used. Among them, Al
It is preferable to use a glass substrate such as an alloy substrate or crystallized glass. This substrate has a ring shape with a hole in the center.

In the manufacturing process of the magnetic disk, the substrate is usually washed and dried first. In the present invention, from the viewpoint of ensuring the adhesion of each layer, washing and drying are performed before the formation. Is desirable.

In manufacturing the magnetic recording medium of the present invention,
It is preferable to form a nonmagnetic metal coating layer such as NiP on the surface of the nonmagnetic substrate.

As a technique for forming the nonmagnetic metal coating layer, there are electroless plating, sputtering, vacuum deposition,
A method used for forming a thin film such as a CVD method can be used. In the case of a substrate made of a conductive material, it is possible to use electrolytic plating. The thickness of the nonmagnetic metal coating layer may be 50 nm or more. However, considering the productivity of the magnetic disk medium, etc.
It is preferably not more than 000 nm. More preferably, it is 100 nm or more and 15,000 nm or less.

The substrate surface or the substrate surface on which the non-magnetic metal coating layer is formed may be subjected to texturing, for example, concentric texturing. Concentric texturing is, for example, mechanical texturing using loose abrasive grains and texture tape, texturing using laser light, or the like, or by polishing them together in the circumferential direction, in the circumferential direction of the substrate. To form a large number of microgrooves.

As the type of free abrasive grains for mechanical texturing, diamond abrasive grains, particularly those whose surfaces have been subjected to a graphitization treatment, are preferred. Alumina abrasive grains are widely used as abrasive grains used in mechanical texturing, but diamond abrasive grains have extremely good performance, especially from the viewpoint of orienting the axis of easy magnetization along the texturing grooves. Demonstrate. The cause is not clear at this time,
Extremely reproducible results have been obtained.

The surface of the substrate does not basically affect the effect of the present invention no matter what value the surface roughness (Ra) takes, but the fact that the head flying height is as small as possible is necessary for realizing high density magnetic recording. Is effective, and one of the features of these substrates is excellent surface smoothness.
a is preferably 2 nm or less, more preferably 1 nm or less, and particularly preferably 0.5 nm or less. However, this Ra shall mean the case where it measures using the stylus type surface roughness meter. At this time, the tip of the needle for measurement has a radius of about 0.2 μm.

An intermediate layer such as a Cr layer, a Cr alloy layer containing Cr as a main component, a chromium oxide layer, or a Cu layer may be formed on the nonmagnetic substrate or the nonmagnetic coating layer of Ni-P or the like, if necessary. After formation, a magnetic layer is formed.

As the intermediate layer, in addition to the pure Cr layer, V and V are added for the purpose of crystal matching with the magnetic layer.
Ti, Mo, Zr, Hf, Ta, W, Ge, Nb, S
An alloy layer to which second and third elements such as i, Cu, and B are added, and a Cr oxide layer are preferable. Above all, pure Cr layer, Ti, M
A Cr alloy layer containing o, W, V, Ta, Si, Nb, Zr and Hf is preferable. The content of the second and third elements varies depending on the respective elements, but is generally 1 atomic% to 50 atomic%, preferably 5 atomic% to 30 atomic%, more preferably 5 atomic% to 20 atomic%. Atomic% range.

The thickness of the intermediate layer may be any thickness that is sufficient to exhibit anisotropy, and is usually 0.1 to 50 nm, preferably 0.3 to 30 nm, and more preferably 0.5 to 30 nm. 10 nm. Substrate heating may or may not be performed when forming a metal film containing Cr as a main component.

The magnetic layer is usually made of pure Co or Co-
P, Co-Ni-P, Co-Ni, Co-Sm, Co-
Cr-Ta, Co-Ni-Cr, Co-Ni-Pt, C
It is preferable to use a Co alloy magnetic material generally used as a magnetic material such as o-Cr-Pt or Co-Cr-Ta-Pt. Ni, Cr, P
A material to which an element such as t, Ta, W, or B or a compound such as SiO ₂ is added may be used. The thickness of the Co alloy magnetic layer is arbitrary, but is usually 10 to 100 nm, preferably 30 to 70 nm.
It is.

The magnetic layer may have a laminated structure of two or more types. An intermediate layer of non-magnetic CoCr or the like may be provided between the underlayer containing Cr as a main component and the magnetic layer.

The film forming method for forming each layer of the magnetic recording medium is arbitrary. For example, physical vapor deposition methods such as direct current (magnetron) sputtering, high frequency (magnetron) sputtering, ECR sputtering, and vacuum deposition are used. No.

The conditions for the film formation are not particularly limited, and the ultimate vacuum, the substrate heating method and the substrate temperature, the sputtering gas pressure, the bias voltage, etc. may be appropriately determined by the film forming apparatus. For example, in the case of sputtering film formation, usually, the ultimate vacuum degree is 1 × 10 ⁻⁶ Torr or less, the substrate temperature is from room temperature to 400 ° C., and the sputtering gas pressure is 1 × 1.
0 ^{−3 to} 20 × 10 ⁻³ Torr, and the bias voltage is generally 0 to −500V.

In film formation, it is generally preferable to heat the nonmagnetic substrate to about 100 to 350 ° C. in order to promote the segregation of Cr in the magnetic layer. Substrate heating may be performed before the formation of the underlayer, and when a transparent substrate having a low heat absorption is used, an underlayer containing Cr as a main component is formed in order to increase the heat absorption. Heat the substrate and then C
An o-alloy magnetic layer may be formed.

On this magnetic layer, a protective layer is formed by a method such as vapor deposition, sputtering, plasma CVD, ion plating, or a wet method, and then a lubricating layer is formed. Examples of the protective layer include carbonaceous layers such as C (carbon), hydrogenated C, nitrogenated C, Amorphous C, SiC, and TiC, and SiO ₂ and Zr _2.
Although a commonly used protective layer material such as an oxide such as O ₃ and Al ₂ O ₃ and a nitride such as SiN and TiN can be used, C or hydrogenated C is preferable. Note that the protective layer may be composed of two or more layers. The thickness of the protective layer is 1
-50 nm, particularly preferably 5-30 nm. Examples of the lubricant used for the lubricating layer include a fluorine-based lubricant, a hydrocarbon-based lubricant, a mixture thereof, and the like, and usually form the lubricating layer with a thickness of 1 to 4 nm.

A magnetic recording apparatus according to the present invention includes the magnetic recording medium according to the present invention, a magnetic head, and means for moving the magnetic head.

The magnetic recording device includes a shaft for fixing one or more magnetic recording media in a skewered manner,
A motor for rotating a magnetic recording medium joined to the shaft via a bearing, a magnetic head, a head arm to which the head is attached, and moving the head to an arbitrary position on the magnetic recording medium via the head arm An example is a magnetic recording device having an actuator that can be driven.

By constructing the reproducing section of the above-mentioned magnetic head with an MR head, a sufficient signal intensity can be obtained even at a high recording density, and 2 G / inch 2 can be obtained.
It is possible to realize a magnetic recording device having a high recording density of bits or more. Also, the magnetic head is used with a flying height of 0.
When flying at a height lower than the conventional height of not less than 01 μm and less than 0.05 μm, the output is improved and a high device S / N is obtained, and a large-capacity and high-reliability magnetic recording device can be provided. The recording density can be further improved by combining a signal processing circuit based on the maximum likelihood decoding method. For example, when recording / reproducing at a recording density of not less than 10 kTPI, not less than linear recording density of 200 kFCI, and not less than 2 Gbits per square inch, Also obtains a sufficient S / N ratio.

The reproducing portion of the magnetic head is composed of a plurality of conductive magnetic layers which generate a large resistance change due to a relative change in their magnetization directions due to an external magnetic field, and a conductive layer disposed between the conductive magnetic layers. The signal strength can be further increased by using a GMR head made of a conductive non-magnetic layer or a GMR head using the spin valve effect, so that the signal strength is 3 Gbits / sq.
A highly reliable magnetic recording device having a linear recording density equal to or higher than CI can be realized.

[0048]

As described above, according to the present invention, it is possible to form a servo signal record having a large reproduction output and a small noise, thereby enabling high-accuracy tracking. Also, unlike the DC magnetization, the use of a high-frequency signal current as the servo signal write current has little dependence on the unevenness of the servo signal recording portion and the write current value, and selectively magnetizes only the magnetic layer of the convex portion. Can be done.

According to the present invention, it is possible to increase the recording density by reducing the track pitch of the magnetic recording medium.

[Brief description of the drawings]

FIG. 1 is a schematic perspective sectional view showing a configuration near a servo signal recording section of a magnetic recording medium according to an embodiment.

FIG. 2 is a schematic cross-sectional view taken along line II-II of FIG. 1 and a reproduced signal waveform diagram.

FIG. 3 is a perspective view showing a conventional example.

FIG. 4 is a sectional view showing a conventional example.

FIG. 5 is an explanatory diagram showing a conventional example.

FIG. 6 is an explanatory diagram showing a conventional example.

FIG. 7 is a cross-sectional view of a projection showing another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,10 Substrate 2,11 Magnetic layer 3,16 Recording track 4 Groove part 7,12 Convex part 13 Magnetic head

Claims (5)

[Claims] 1. A servo signal recording portion of a recording track is composed of a concave portion and a convex portion, and a servo signal is recorded on a magnetic layer on a surface of the convex portion such that a magnetization direction becomes a longitudinal direction of a data recording track. The magnetic recording medium according to claim 1, wherein the servo signal is recorded such that the magnetization direction is reversed at least once in a magnetic layer on one protrusion. 2. The magnetic recording medium according to claim 1, wherein the magnetization direction is reversed a plurality of times. 3. The magnetic recording medium according to claim 2, wherein the magnetization direction is reversed three times or more. 4. A servo signal recording method for writing a servo signal by a magnetic head on a magnetic layer on the convex portion of the magnetic recording medium according to claim 1, wherein the magnetic head comprises one of the magnetic heads. A servo signal writing current to the magnetic head being a high-frequency signal current so that the direction of a magnetic flux generated from the magnetic head is reversed at least once while traversing the convex portion in the longitudinal direction of the data recording track. Signal recording method. 5. A magnetic recording apparatus comprising: a magnetic recording medium; driving means for the magnetic recording medium; a magnetic head; and means for moving the magnetic head in a direction crossing a data recording track of the magnetic recording medium. Claim 1 is a magnetic recording medium.
4. A magnetic recording device, which is the magnetic recording medium according to any one of items 3 to 3.