JP2001312808A - Magnetic disk, method for forming its magnetization pattern and magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic disk in which a servo mechanism for positioning the head of a high density magnetic disk device can be precisely and easily applied and high density recording is permitted and to provide a magnetic disk device. SOLUTION: In the magnetic disk having at least one magnetic layer provided on a substrate, plural radial direction magnetization regions each consisting of a magnetic domain whose magnetization direction is a radial direction and an outer peripheral direction and a magnetic domain whose magnetization direction is a radial direction and an inner peripheral direction are provided at an interval of nearly equal angle in the magnetic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk used for information recording, a method of forming a magnetic pattern thereof, and a magnetic disk device using the same.

[0002]

2. Description of the Related Art Magnetic disk devices (hard disk drives, HDDs) are widely used as external recording devices for information processing devices such as computers, and in recent years are also used as moving image recording devices and recording devices for set-top boxes. It is getting. A magnetic disk device generally includes a shaft for fixing one or more magnetic disks in a skewered manner, a motor for rotating a magnetic disk joined to the shaft via bearings, and a magnetic disk used for recording and / or reproduction. It comprises a head, an arm to which the head is attached, and an actuator that can move the head to an arbitrary position on the magnetic disk via the head arm. The recording / reproducing head is usually a flying head, and moves on a magnetic disk at a constant flying height. In addition to the flying head, use of a contact head (contact type head) has been proposed in order to further reduce the distance from the medium.

A magnetic disk mounted on a magnetic disk device generally has a NiP layer formed on the surface of a substrate made of an aluminum alloy or the like, performs a required smoothing process, texturing process, and the like, and then forms a metal layer thereon. It is manufactured by sequentially forming an underlayer, a magnetic layer (recording layer, information recording layer), a protective layer, a lubricating layer, and the like. Alternatively, it is manufactured by sequentially forming a metal base layer, a magnetic layer (recording layer, information recording layer), a protective layer, a lubricating layer, and the like on the surface of a substrate made of glass or the like. Magnetic disks include in-plane magnetic disks and perpendicular magnetic disks. The longitudinal recording in which the magnetization direction is the circumferential direction is usually performed on the in-plane magnetic disk.

[0004] The density of magnetic disks has been increasing year by year, and there are various techniques for realizing this. For example, improvements such as reducing the flying height of the magnetic head, employing a GMR head as the magnetic head, increasing the magnetic material used for the recording layer of the magnetic disk to have a high coercive force, and improving the information recording track of the magnetic disk Attempts have been made to reduce the distance between the two. For example, 100Gb
To realize it / inch ² , the track density is 10
0 ktpi or more is required.

[0005]

On each track, a control magnetization pattern for controlling the magnetic head is formed. For example, it is a signal used for position control of the magnetic head or a signal used for synchronization control. When the number of tracks is increased by reducing the interval between information recording tracks, a signal used for position control of a data recording / reproducing head (hereinafter, “servo signal”) is used.
I may say. ) Must also be provided densely in the radial direction of the disk, that is, more, so that precise control can be performed.

It is also desired to increase the data recording capacity by reducing the area other than the area used for data recording, that is, the area used for servo signals and the gap between the servo area and the data recording area to increase the data recording area. There is a great demand. For this purpose, it is necessary to increase the output of the servo signal and the accuracy of the synchronization signal.

In the magnetic disk of the differential signal detection system, in order to increase the reproduction signal from the servo pattern, the density of the servo pattern in the track direction (FC
It is necessary to increase I) to increase the integrated amount of the differential signal obtained per unit distance. In the case of a coarse servo pattern, the amount of integration of the differential signal is indispensable, so that the reproduced signal is small, and it is difficult to perform accurate positioning. Therefore, high-density and precise recording is required in the track direction.

Conventionally, as a means for forming such a fine servo signal on a disk, a method of writing a servo signal while positioning the magnetic head at a precise radial position using a magnetic head used for recording and reproducing information is conventionally used. However, this requires expensive equipment and takes a long time to write, so masks (master disk, master) can be obtained by magnetic transfer or optical transfer technology using both heat (light) and magnetism. A method of transferring a servo pattern formed on a disk onto a disk has been proposed.

One example is a method in which a servo pattern is formed on a master disk having a magnetic layer having a high coercive force, the master disk is brought into close contact with the magnetic disk, and a magnetization pattern is transferred by applying an auxiliary magnetic field from outside (USP).
5,991,104).

In another example, the medium is magnetized in one direction in advance, and a soft magnetic layer or the like having a high magnetic permeability and a low coercive force is patterned on the master disk so that the master disk is brought into close contact with the medium and an external magnetic field is applied. Is the way. The soft magnetic layer functions as a shield, and a magnetization pattern is transferred to an unshielded region (EP915456). This technology uses a master disk to form a magnetization pattern on a medium by a strong magnetic field.

The above transfer technique is excellent in that a magnetic pattern having a complicated shape that cannot be recorded by a magnetic head can be formed. However, since the transfer is performed by performing fine processing on a mask (master), there is a restriction on the minimum dimension of the pattern. Was. Furthermore, in the optical transfer technology using both heat (light) and magnetism, it is common to transfer the image with a distance between the mask and the magnetic disk, and thus the pattern may be blurred due to light diffraction.
In this respect, the minimum size of the magnetic pattern that can be formed is limited. Therefore, in order to apply the transfer technique to a magnetic disk having a high track density, it is essential to solve this point.

In a normal burst servo medium, it is the side of the recording section (radial end of the magnetic domain) that is used for position detection and the center of the recording section (radial direction of the magnetic domain) used for information recording. Not relatively central). Generally, the recording portion side is not magnetically saturated and the output signal is unstable, so that there is a problem that high noise is generated, and there is a problem that high-precision positioning is difficult. Therefore, a servo pattern in which the magnetization direction is a radial direction has been proposed. For example, Japanese Patent Application Laid-Open No. H7-161021 discloses a medium having two magnetic layers, in which a servo pattern having a radial magnetization is recorded in a lower layer and an information pattern having a circumferential magnetization is recorded in an upper layer. A magnetic disk is described. Servo patterns are continuously recorded in the lower layer in the circumferential direction. Based on this, the position of the magnetic head is controlled, and an information pattern having circumferential magnetization is recorded in the upper layer. However, adding another magnetic layer under the magnetic layer for information recording is not preferable in controlling the crystal orientation of the magnetic layer for information recording. Since the control of the crystal orientation is more important for a high-density magnetic disk having a higher linear recording density, increasing the number of layers increases the surface roughness of the medium, which is not preferable, and also causes an increase in cost. Further, since the distance between the lower layer and the magnetic head is increased by the thickness of the upper layer, the resolution of the signal from the servo pattern recorded in the lower layer is reduced. For this reason, it is difficult to perform fine tracking and is not suitable for a high-density magnetic disk having a narrow track pitch. Further, when the track pitch becomes narrow, the recording frequency of the lower servo pattern must be increased, and a signal having a frequency similar to the recording frequency of the upper information pattern may be output from the servo pattern. Therefore, for example, a track density of 10 kTPI or more, a linear recording density of 200 kFCI or more,
There has been a demand for obtaining a magnetization pattern suitable for a high-density magnetic disk having a recording density of 2 Gbits per square inch or more. Japanese Patent Application Laid-Open No. Sho 56-145568 discloses that a servo pattern consisting of radial magnetization is formed continuously in the circumferential direction, and the magnetization has the same magnitude at the same radius, and is triangular or sinusoidal in the radial direction. A magnetic disk in which the magnitude of magnetization changes in a wave-like manner is described. However, a magnetic disk device using this medium uses one of a plurality of recording surfaces as a reference surface (servo surface) for positioning, and a servo head dedicated to positioning is provided on a servo track previously recorded on this servo surface. This is a magnetic disk device that performs tracking and thereby simultaneously performs tracking on another recording surface (servo surface servo method). That is, one side on which the servo pattern is provided is used only for tracking servo, and cannot be used for information recording.
However, at present, the size and capacity of magnetic disk drives are increasing, and the disadvantage that one side cannot be used for information recording is significant.
This method is not adopted. Further, since the servo head dedicated to positioning is tracked by the position information on the servo surface, and the head on the other surface is tracked indirectly based on the tracking information, the positioning accuracy is not very high, and the track density is 10%.
It is not sufficient for use with a high-density magnetic disk having a kTPI or more. It should be noted that none of the above documents describes a servo pattern recording method. The present invention solves these problems, and is particularly suitable for a high-density magnetic disk, and a magnetic disk capable of performing accurate positioning on tracks arranged at a high density while having a coarse servo pattern. It is an object of the present invention to provide a method for forming a magnetization pattern and a magnetic disk drive.

[0013]

In view of the above situation, the inventors of the present invention have made intensive studies and found that the magnetic layer of the magnetic disk is placed in an in-plane direction (radial direction) perpendicular to the recording direction (circumferential direction). Radial magnetization region with magnetization direction (orthogonal magnetization region)
Are provided at substantially equal angular intervals and are used as position detection patterns, whereby even a high-density magnetic disk can be positioned at a high resolution with a coarse magnetization pattern, and the present invention has been achieved.

That is, the gist of the present invention is a magnetic disk having at least one magnetic layer provided on a substrate, wherein the magnetic layer has a magnetic domain whose magnetization direction is a radial direction and an inner circumferential direction and a magnetization direction. A magnetic disk is characterized in that a plurality of radial magnetization regions (orthogonal magnetization portions) formed of magnetic domains that are radial and outer circumferential directions are provided at substantially equal angular intervals. In this medium, the circumferential direction is the recording direction, and the relative movement direction (track direction) between the medium and the recording / reproducing head.
It is. Another gist of the present invention is that a pattern provided on a mask is transferred by applying an external magnetic field to a magnetic disk having at least one magnetic layer provided on a substrate, so that the magnetization direction has a radius on the magnetic layer. There is provided a method for forming a magnetization pattern, characterized by providing a magnetization pattern which is a direction. Still another aspect of the present invention is a magnetic disk, a driving unit that drives the magnetic disk in a recording direction, a magnetic head including a recording unit and a reproducing unit, and a unit that relatively moves the magnetic head with respect to the magnetic disk. A magnetic disk device having a recording / reproducing signal processing unit for performing a recording signal input to a magnetic head and a reproducing signal output from the magnetic head,
The magnetic disk device according to the present invention is characterized in that the magnetic disk is any one of the above magnetic disks and includes means for controlling a radial position of the magnetic head based on the magnetization pattern.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The magnetic disk of the present invention is a magnetic disk having at least one magnetic layer provided on a substrate, wherein the magnetic layer has a magnetic domain whose magnetization direction is a radial direction and an inner circumferential direction and a magnetic domain whose magnetization direction is a radial direction and an outer circumferential direction. Radially magnetized regions (orthogonal magnetized portions) composed of magnetic domains, which are directions, are provided at substantially equal angular intervals.

Since the radial magnetization region of the present invention has both the inner circumferential magnetic domain and the outer circumferential magnetic domain, a magnetic domain boundary exists between the two magnetic domains. The magnetization of the orthogonal magnetized portion itself is not detected by a normal magnetic head, but a magnetic field generated from a magnetic domain boundary in the orthogonal magnetized portion and perpendicular to the medium surface is detected. Therefore, the signal can be read. Moreover,
The separation from the information signal is easy, and the positioning of the magnetic head can be easily performed. Further, since a magnetic field in the vertical direction is always generated along the boundary and the output signal is continuously obtained, the integrated value of the output signal becomes large and a large reproduction signal is easily obtained. Therefore, a highly accurate magnetic head can be positioned even with a coarse servo pattern. Since the orthogonal magnetization part is magnetically saturated, there is an advantage that the output signal is stable and the noise is small.

In addition, a radial magnetization region (orthogonal magnetization portion)
Are provided at substantially equal angular intervals rather than continuously, tracking is performed intermittently in the orthogonal magnetization portion, and other regions can be used for information recording (sector servo method). For example, a radial magnetization region serving as a servo pattern and a circumferential magnetization region serving as an information pattern can be provided alternately in the circumferential direction. Therefore, unlike the conventional case, there is no need to provide two magnetic layers and one layer dedicated to servo pattern recording, and the present invention can be preferably applied to an ordinary magnetic disk having only one magnetic layer. Alternatively, the recording surface is not wasted unlike the servo surface servo method. Further, since the head for reading the position signal and the head for recording the information are the same, tracking can be performed with high accuracy even with a high-density magnetic disk. Therefore, the present invention provides, for example, a track density of 10 kTPI or more and a linear recording density of 200
The present invention can be preferably applied to a high-density magnetic disk having a recording density of not less than kFCI and not less than 2 Gbits per square inch. Each servo pattern is formed, for example, radially or curvedly radially. Such servo patterns are provided, for example, on the order of several tens to several hundreds in one round, at substantially equal angular intervals. The substantially equiangular intervals include, for example, an error of about several μm to several tens μm. Most preferably, the servo patterns are provided at exactly equal angular intervals without error. Although the case where the magnetization pattern is a servo pattern has been described above, the servo pattern may be a servo pattern for controlling the position of the recording / reproducing magnetic head or a reference pattern for recording the servo pattern. There may be. In the latter case, the reference pattern is read by a magnetic head later, and another servo pattern is recorded based on the reference pattern. In addition, the magnetization pattern may include address information, synchronization information, and the like as needed.

The reproduction principle of the present invention will be described. In the case of an in-plane magnetic disk, the magnetization is in-plane and oriented in the same direction as the track direction of the medium, and the magnetic head detects a leakage magnetic field from the boundary between magnetic domains. The magnetic head usually has a structure in which only magnetic domains in the track direction are detected, and magnetic domains in the radial direction perpendicular to the magnetic domains are not detected. However, the magnetic field in the vertical direction can be detected. When a magnetic domain is formed in the radial direction, a magnetic field in the direction perpendicular to the disk surface is generated in a portion where the magnetization is reversed, that is, in a narrow region near the boundary of the magnetic domain. In the present invention, using this, the servo pattern is recorded as a radial magnetization region (orthogonal magnetization portion), and a magnetic domain boundary portion between an inner circumferential magnetic domain and an outer circumferential magnetic domain of the orthogonal magnetization portion (hereinafter, simply referred to as a magnetic domain boundary portion). ) Is detected to obtain a servo signal. Since the signal of the orthogonal magnetization part itself is not detected, the magnetization other than the magnetic domain boundary does not affect the signal output. As shown in FIG. 4, in the orthogonal magnetized portion, at the boundary between the individual magnetic domains, the vertical direction (N
Or, there is a magnetic field of S). This is detected by the magnetic head.

In the present invention, preferably, the magnetic domain boundary portion of the radial magnetization region (orthogonal magnetization region) is displaced in the radial direction, that is, is changed so as to cross the recording direction. For example, at least a part of the magnetic domain boundary portion is displaced in the radial direction like a step. At this time, the width of the step-like displacement is preferably in the range of 1/8 to 3/8 of the repetition period of the unit pattern in the radial direction. Particularly preferably, 1/6, 1/4, 1/3
Is one of Alternatively, the magnetic domain boundary portion has a portion displaced in a substantially triangular wave shape with respect to the radius. The substantially triangular wave shape
Including a shape in which the top of the triangle wave is rounded instead of the exact triangle wave, for example. By performing such displacement, signals having different phases can be obtained in one area, so that when tracking is lost, the direction can be determined.
Sufficient information for tracking is easily obtained even with a short servo pattern. For this reason, the servo pattern area can be reduced, and the area that can be used for information recording increases accordingly, and the recording capacity can be increased. next,
A method of providing a magnetic pattern having a radial magnetization direction on a magnetic layer of a magnetic disk will be described. For such a radial magnetization, when a magnetic head is used to form a radial magnetization region, it is necessary to manufacture a special head in which the magnetization direction is the radial direction. Therefore, it is preferable that the pattern is formed by applying an external magnetic field and transferring the pattern provided on the mask. For example, a magnetic transfer method or an optical transfer method using heating and magnetism, which will be described in detail later. In the magnetic transfer method, first, substantially the entire magnetic layer is uniformly magnetized in one radial direction (for example, the inner circumferential direction). Thereafter, a mask (master disk) in which the soft magnetic layer is patterned according to the magnetization pattern to be formed is brought into close contact with the medium, and an external magnetic field (for example, in the outer circumferential direction) that is larger than the coercive force of the medium in a direction opposite to the previous magnetization. multiply. The soft magnetic layer acts as a shield, and the unshielded region is magnetized in the direction of the external magnetic field. As a result, in the magnetic layer, radial magnetization regions including magnetic domains whose magnetization directions are radial and inner circumferential directions and magnetic domains whose magnetization directions are radial and outer circumferential directions are formed at substantially equal angular intervals. In the optical transfer method, first, almost the entire magnetic layer is uniformly magnetized in one radial direction (for example, the inner circumferential direction). Thereafter, a weak external magnetic field (for example, in the outer circumferential direction) is applied in the direction opposite to the previous magnetization while irradiating energy rays through a mask in which the transmission portion and the non-transmission portion are patterned according to the magnetization pattern to be formed. Is the way. The region heated by the energy beam to a temperature higher than the magnetization extinction temperature is magnetized in the direction of the external magnetic field, and as a result, magnetization patterns are formed at substantially equal angular intervals. In the present invention, a region where a magnetization pattern is formed by two types of magnetization in the radial direction is defined as a radial magnetization region. The other regions uniformly magnetized in the inner circumferential direction are not included. Since such a region does not include a magnetic domain boundary, it does not generate a signal that can be detected by a normal magnetic head. Such an area becomes an information recording area for recording information (data) later. The initial uniform magnetization may be a part of the magnetic layer instead of the entire magnetic layer. For example, uniform magnetization may be performed only in a region desired to be a radial magnetization region. As described above, according to the magnetic transfer method or the optical transfer method, once a pattern is formed on a mask (master disk) according to the magnetization pattern to be formed, and the direction of application of the external magnetic field is set to the radial direction, the radius can be easily changed. A directional magnetization region can be formed, which is preferable. In general, in the transfer method, it is difficult to form a finer magnetic pattern as in a magnetic head, but the radial magnetization pattern according to the present invention is a relatively coarse pattern, and a sufficient signal can be obtained. Furthermore, according to the optical transfer method, since it is not necessary to use an external magnetic field larger than the coercive force of the medium, it is easy to form a magnetization pattern even in a high-density medium having a high coercive force suitable for high-density recording. preferable. For example, it can be easily applied to a magnetic disk having a coercive force at room temperature of 2000 Oe or more. That is, according to the optical transfer method, since local heating and application of an external magnetic field are combined in forming a magnetization pattern, it is not necessary to use a strong external magnetic field. Then, even if a magnetic field is applied to a region other than the heating region, the region is not magnetized, so that magnetic domain formation can be limited to the heating region. Therefore, a magnetic domain boundary becomes clear, a magnetization transition width is small, and a magnetic transition at the magnetic domain boundary is very steep, so that a pattern with high output signal quality can be formed. Since there is no need to crimp the medium (magnetic disk) and the master disk, there is no risk of damaging the medium or the mask and increasing defects of the medium. Since no irregularities are formed on the medium and there is no increase in scratches or defects, the surface roughness of the medium can be suppressed to a small value, and the traveling of the magnetic head that flies and contacts does not become unstable.

The optical transfer method will be described in more detail. In the first uniform magnetization, a strong external magnetic field is applied to the magnetic disk to uniformly magnetize the entire magnetic layer in a desired radial direction. As a means for applying the external magnetic field, a magnetic head may be used, or a plurality of electromagnets or permanent magnets may be arranged so as to generate a magnetic field in a desired magnetization direction. Further, these different means may be used in combination. The strength of the magnetic field depends on the characteristics of the magnetic layer of the magnetic disk, and it is preferable that the magnetic layer is magnetized by a magnetic field that is at least twice the coercive force of the magnetic layer at room temperature. If it is lower than this, the magnetization may be insufficient. However, usually, the coercive force of the magnetic layer at room temperature is about 5 times or less due to the capability of the magnetizing device used for applying the magnetic field. Next, the surface of the magnetic layer of the magnetic disk is partially heated to raise the temperature to near the magnetization disappearance temperature of the magnetic layer, for example, the Curie temperature, and at the same time, an external magnetic field is applied so as to be magnetized in a direction opposite to the uniform magnetization. Apply. The stronger the strength of the magnetic field, the easier the magnetization pattern is formed. Preferably, the magnetic field is at least 1/8 of the coercive force of the magnetic layer at room temperature.
If it is lower than this, the heating section may be magnetized again in the same direction as the surroundings under the influence of the magnetic field from the surrounding magnetic domains during cooling.

The magnetic field is smaller than the coercive force of the magnetic layer at room temperature. The coercive force of the magnetic layer at room temperature is preferably ２ or less, more preferably １ ／ or less. If it is larger than this, the magnetic domains around the heating section may be affected. The heating may be performed at a temperature at which the coercive force of the magnetic layer is reduced. For example, the heating is near the magnetization disappearance temperature or the Curie temperature of the magnetic layer. Preferably, it is heated to 100 ° C. or higher. Magnetic layers that are affected by an external magnetic field below 100 ° C. tend to have low domain stability at room temperature. Further, the heating temperature is preferably 700 ° C. or lower.
If the heating temperature is too high, the magnetic layer may be deformed.

Next, a method for locally heating the magnetic layer will be described. The heating means only needs to have a function capable of partially heating the surface of the magnetic layer, but in consideration of prevention of heat diffusion to unnecessary parts and controllability, power control, the size of the portion to be heated can be easily controlled. It is preferable to use an energy ray such as a laser. At this time, it is preferable to use a mask together. By irradiating the energy beam through the mask, a plurality of magnetization patterns can be formed at a time, so that the magnetization pattern formation process is short and simple.

Further, it is preferable to control the heating portion and the heating temperature by making the energy beam more pulse-shaped than continuous irradiation. In particular, use of a pulse laser light source is preferred.
A pulsed laser light source oscillates a laser intermittently in a pulsed manner. Compared to a continuous laser which is intermittently pulsed by an optical component such as an acousto-optic device (AO) or an electro-optic device (EO), it is pulsed. It is very preferable that a laser having a high power peak value can be irradiated in a very short time and heat is hardly accumulated. When a continuous laser is pulsed by an optical component, the pulse has substantially the same power over the pulse width. On the other hand, the pulse laser light source accumulates energy by resonance in the light source and emits the laser at once as a pulse, so that the peak power is very large within the pulse and then decreases. In the present invention, in order to form a magnetization pattern with high contrast and high accuracy,
The use of a pulsed laser light source is suitable because it is preferable to rapidly heat and then rapidly cool in a very short time.

It is preferable that the medium surface on which the magnetization pattern is formed has a large temperature difference between when the pulsed energy beam is irradiated and when it is not irradiated, in order to increase the pattern contrast or the recording density. Therefore, it is preferable that the temperature be lower than room temperature when the pulsed energy beam is not irradiated. Room temperature is about 25 ° C. When a pulsed energy beam is used, an external magnetic field may be applied continuously or in a pulsed manner.

The wavelength of the energy ray is preferably 1100 nm or less. If the wavelength is shorter than this, the diffraction effect is small and the resolution is increased, so that a fine magnetization pattern is easily formed. More preferably, the wavelength is 600 nm or less. In addition to high resolution, there is an advantage that the spacing between the mask and the magnetic disk is widened due to the small diffraction, the handling is easy, and the magnetization pattern forming apparatus is easy to configure. The wavelength is 1
It is preferably at least 50 nm. If it is less than 150 nm, the absorption of the synthetic quartz used for the mask becomes large, and the heating tends to be insufficient. If the wavelength is 350 nm or more, optical glass can be used as a mask.
Specifically, an excimer laser (157 nm, 193n)
m, 248 nm, 308 nm, 351 nm. Especially KrF
248 nm is often used), the second harmonic (532 nm), the third harmonic (355 nm), or the fourth harmonic (266 nm) of the YAG Q-switched laser (1064 nm), Ar
Laser (488 nm, 514 nm), ruby laser (6
94 nm).

The power of the energy ray may be selected at an optimum value according to the magnitude of the external magnetic field, but the power per pulse of the pulsed energy ray is 1000 mJ / cm ^2.
It is preferable to set the following. If a power larger than this is applied, the surface of the magnetic disk may be damaged and deformed by the pulsed energy beam.

It is more preferably at most 500 mJ / cm ² , still more preferably at most 200 mJ / cm ² .
In this region, a magnetization pattern with high resolution is easily formed even when a substrate having relatively large thermal diffusion is used. Further, the power is preferably set to 10 mJ / cm ² or more. If it is smaller than this, the temperature of the magnetic layer hardly rises and magnetic transfer hardly occurs.

If there is a concern that the medium may be damaged by the energy beam, it is possible to take measures such as reducing the power of the pulsed energy beam and increasing the intensity of the magnetic field applied simultaneously with the pulsed energy beam. . For example, in the case of an in-plane magnetic disk, the coercive force at room temperature is 25%.
In the case of perpendicular recording, a magnetic field as large as 1 to 50% is applied to lower the irradiation energy.

The pulse width of the pulse energy beam is 1 μm.
sec or less is desirable. If the pulse width is wider than this, the heat generated by the energy given to the magnetic disk by the pulsed energy beam is dispersed, and the resolution tends to decrease. When the power per pulse is the same, a shorter pulse width and irradiation with strong energy at one time tend to reduce thermal diffusion and increase the resolution of the magnetization pattern. More preferably, it is 100 nsec or less. In this region, a magnetization pattern with high resolution is easily formed even when a substrate such as Al having a relatively large thermal diffusion of a metal is used. When forming a pattern having a minimum width of 2 μm or less,
The pulse width is preferably set to 25 nsec or less. That is, if importance is placed on the resolution, the shorter the pulse width, the better. Also, the pulse width is preferably 1 nsec or more. This is because it is preferable to maintain the heating until the magnetization reversal of the magnetic layer is completed.

As one type of pulsed laser, there is a laser which can generate picosecond and femtosecond level ultrashort pulses at a high frequency, such as a mode-locked laser. During the period of irradiating the ultrashort pulse at a high frequency, the laser is not irradiated for a very short time between each ultrashort pulse, but the heating portion is hardly cooled because it is a very short time.
That is, the region once heated to the Curie temperature or higher is maintained at the Curie temperature or higher.

Therefore, in such a case, the continuous irradiation period (the continuous irradiation period including the time during which the laser is not irradiated between the ultrashort pulses) is defined as one pulse. In addition, the integral value of the irradiation energy amount during the continuous irradiation period is calculated as power per pulse (mJ /
cm ² ).

Next, a preferred configuration of a magnetic disk to which the present invention is applied will be described. As the substrate of the magnetic disk of the present invention, it is necessary that the substrate does not vibrate even when rotated at high speed during high-speed recording and reproduction, and a hard substrate is usually used. In order to obtain sufficient rigidity to prevent vibration, the thickness of the substrate is generally 0.1 mm.
3 mm or more is preferable. However, if it is thick, it is disadvantageous for thinning the magnetic recording device, so that it is preferably 3 mm or less. For example, Al
An Al alloy substrate such as an Al-Mg alloy containing Mg as a main component, or an Mg alloy such as an Mg-Zn alloy containing Mg as a main component.
An alloy substrate, a substrate made of any of ordinary soda glass, aluminosilicate glass, amorphous glass, silicon, titanium, ceramics, various resins, a substrate obtained by combining them, or the like can be used. Among them, Al alloy substrates and glass substrates such as crystallized glass in terms of strength,
It is preferable to use a resin substrate in terms of cost.

In the manufacturing process of the magnetic disk, it is usual to wash and dry the substrate first, and in the present invention, from the viewpoint of ensuring the adhesion of each layer, it is necessary to wash and dry the substrate before its formation. Is desirable. Ni on the substrate surface
A metal layer such as P or NiAl may be formed. When the metal layer is formed, a method used for forming a thin film such as an electroless plating method, a sputtering method, a vacuum evaporation method, and 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 metal layer is preferably 50 nm or more. However, in consideration of the productivity of the magnetic disk medium and the like, the thickness is preferably 20 μm or less. More preferably, it is 10 μm or less.

The region where the metal layer is formed is desirably the entire region of the substrate surface, but it is also possible to implement only a part, for example, only the region where texturing is to be performed. Also, concentric texturing may be applied to the surface of the substrate or the surface of the substrate on which the metal layer is formed. In the present invention, concentric texturing is, for example, mechanical texturing using free abrasive grains and texture tape or texturing using a laser beam, or by using these together, by polishing in the circumferential direction. This refers to a state in which a large number of microgrooves are formed in the circumferential direction of the substrate. Generally, mechanical texturing is performed to obtain in-plane anisotropy of the magnetic layer. If it is desired to form an in-plane isotropic magnetic layer, it is not necessary to apply the magnetic layer. Generally, texturing using a laser beam or the like is performed by CSS (contact start and
Stop) is performed to improve the characteristics. When the magnetic disk device is of a system (load / unload system) in which the head is retracted outside the disk when the magnetic disk device is not driven, there is no need to apply this method.

The type of free abrasive grains for mechanical texturing is most preferably diamond abrasive grains, especially those whose surfaces are graphitized. Alumina abrasive grains are widely used as abrasive grains for mechanical texturing, but diamond abrasive grains are particularly considered from the viewpoint of the in-plane orientation medium that orients the axis of easy magnetization along the texturing grooves. Has extremely good performance.

It is effective that the head flying height is as small as possible to realize high-density magnetic recording, and one of the features of these substrates is excellent surface smoothness. Therefore, the roughness Ra of the substrate surface is 2 nm or less. And more preferably 1 nm or less. Particularly, the thickness is preferably 0.5 nm or less.
The substrate surface roughness Ra is a value calculated according to JIS B0601 after measuring with a stylus type surface roughness meter at a measurement length of 400 μm. At this time, the tip of the measuring needle has a radius of about 0.2 μm.

Next, an underlayer or the like may be formed between the substrate and the magnetic layer. The underlayer is preferably made of Cr as a main component for the purpose of refining the crystal and controlling the orientation of the crystal plane. As the material of the underlayer containing Cr as a main component, in addition to pure Cr, Cr, V, Ti, Mo, Z may be used for the purpose of crystal matching with the recording layer.
alloys containing one or more elements selected from the group consisting of r, Hf, Ta, W, Ge, Nb, Si, Cu, and B;
Including.

Above all, pure Cr, or Cr, Ti, Mo,
An alloy to which one or more elements selected from W, V, Ta, Si, Nb, Zr and Hf are added is preferable. The optimum content of the second and third elements differs depending on the respective elements, but is generally preferably 1 to 50 atomic%, more preferably 5 to 30 atomic%, and still more preferably 5 to 30 atomic%. % To 20 atomic%.

The thickness of the underlayer may be any thickness which is sufficient to exhibit this anisotropy, but is preferably 0.1 to 50.
nm, more preferably 0.3 to 30 nm, even more preferably 0.5 to 10 nm. The substrate may or may not be heated during the formation of the underlayer mainly composed of Cr. A soft magnetic layer may be provided between the underlayer and the recording layer in some cases. In particular, the effect is large and is preferably used for a keeper medium having little magnetization transition noise or a perpendicular magnetic disk having magnetic domains perpendicular to the plane of the medium.

The soft magnetic layer may have a relatively high magnetic permeability and a small loss, but NiFe or an alloy to which Mo or the like is added as a third element is preferably used. Although the optimum magnetic permeability greatly varies depending on the characteristics of the head and the recording layer used for recording data, it is generally preferable that the maximum magnetic permeability is about 10 to 1,000,000 (H / m).

Alternatively, an intermediate layer may be provided on the underlayer containing Cr as a main component, if necessary. For example, it is preferable to provide a CoCr-based intermediate layer because the crystal orientation of the magnetic layer can be easily controlled. Next, a recording layer (magnetic layer) is formed. Between the recording layer and the soft magnetic layer, a layer of the same material as the underlayer or another nonmagnetic material may be inserted. When forming the recording layer, the substrate may or may not be heated. As the recording layer, C
An o-alloy magnetic layer, a rare earth magnetic layer represented by TbFeCo, a transition metal / noble metal based laminated film represented by a laminated film of Co and Pd, and the like are preferably used.

The Co alloy magnetic layer is usually made of pure Co, CoNi, CoSm, CoCrTa, CoNiCr, C
Co, commonly used as a magnetic material such as oCrPt
Alloy magnetic materials can be used. These Co alloys are further added with N
Elements to which i, Cr, Pt, Ta, W, B or the like, or compounds such as SiO ₂ may be added. For example, CoCrPtT
a, CoCrPtB, CoNiPt, CoNiCrPt
B and the like. The thickness of the Co alloy magnetic layer is arbitrary, but is preferably 5 nm or more, more preferably 10 nm or more. Further, it is preferably 50 nm or less, more preferably 30 nm or less. The recording layer may be formed by laminating two or more layers via an appropriate non-magnetic intermediate layer or directly. At that time, the composition of the magnetic materials to be laminated may be the same or different.

As the rare-earth magnetic layer, a general magnetic material can be used. For example, TbFeCo, Gd
Examples include FeCo, DyFeCo, and TbFe.
Tb, Dy, Ho or the like may be added to these rare earth alloys. Ti, Al, and Pt may be added for the purpose of preventing oxidative deterioration. The thickness of the rare earth magnetic layer is arbitrary, but is usually about 5 to 100 nm. The recording layer may be formed by laminating two or more layers via an appropriate non-magnetic intermediate layer or directly. At that time, the composition of the magnetic materials to be laminated may be the same or different. In particular, the rare earth magnetic layer has an amorphous structure film and has magnetization in a direction perpendicular to the plane of the medium, so that it is suitable for high recording density recording.

Similarly, as the transition metal and noble metal-based laminated film on which perpendicular magnetic recording can be performed, a general magnetic material can be used. For example, Co / Pd, Co / Pt, Fe
/ Pt, Fe / Au, Fe / Ag and the like. The transition metal and the noble metal of these laminated film materials need not be particularly pure, and may be an alloy mainly composed of them. The thickness of the laminated film is arbitrary, but is usually 5 to 1000.
nm. Further, a laminate of three or more materials may be used as necessary.

The coercive force of the magnetic layer at room temperature needs to maintain magnetization at room temperature and be uniformly magnetized by an appropriate external magnetic field. By setting the coercive force at room temperature of the magnetic layer to 2000 Oe or more, a medium that can maintain small magnetic domains and is suitable for high-density recording can be obtained. More preferably 3
000 Oe or more. However, preferably 20 kOe
The following is assumed. If it exceeds 20 kOe, a large external magnetic field is required for collective magnetization, and normal magnetic recording may be difficult to perform.

When the optical transfer method is used, the magnetic layer
It is necessary that the material be magnetized by a weak external magnetic field at an appropriate heating temperature while maintaining the magnetization at room temperature. The larger the difference between the room temperature and the magnetization extinction temperature is, the more easily magnetic domains of the magnetization pattern are formed. Therefore, the magnetization extinction temperature is preferably higher, more preferably 100 ° C. or higher, and more preferably 150 ° C. or higher. For example, there is a magnetization extinction temperature near the Curie temperature (slightly below the Curie temperature) or near the compensation temperature.

The Curie temperature is preferably 100 ° C. or higher. If the temperature is lower than 100 ° C., the stability of the magnetic domain at room temperature tends to be low. It is more preferably at least 150 ° C. Further, the temperature is preferably 700 ° C. or less. If the magnetic layer is heated to an excessively high temperature, the magnetic layer may be deformed. Two or more of these recording layers may be provided to increase the recording capacity. At this time, it is preferable that another layer is interposed therebetween.

It is preferable to form a protective layer on the magnetic layer. That is, the outermost surface of the medium is covered with the hard protective layer. The protective layer functions to prevent the magnetic layer from being damaged by a head, a collision, or a mask between dust and dust. When a transfer method using a mask is applied, it also has a function of protecting the medium from contact with the mask. The protective layer also has the effect of preventing oxidation of the heated magnetic layer. The magnetic layer is generally easily oxidized, and is more easily oxidized when heated. When there are a plurality of magnetic layers, a protective layer may be provided on the magnetic layer near the outermost surface. The protective layer may be provided directly on the magnetic layer, or may have another layer interposed therebetween as required.

The protective layer only needs to be hard and resistant to oxidation. Generally carbon, hydrogenated carbon,
A carbonaceous layer of nitrogenated carbon, amorphous carbon, SiC, or the like, SiO ₂ , Zr ₂ O ₃ , SiN, TiN, or the like is used. The protective layer may be a magnetic material.
In particular, in order to make the distance between the head and the magnetic layer as close as possible, it is preferable to provide a very hard protective layer thinly.
Therefore, a carbonaceous protective film is preferable in terms of impact resistance and lubricity, and diamond-like carbon is particularly preferable. Not only does it play a role in preventing the magnetic layer from being damaged by energy rays, it also becomes extremely resistant to damage to the magnetic layer by the head.
Further, the protective layer may be composed of two or more layers. It is preferable to provide a layer containing Cr as a main component as a protective layer immediately above the magnetic layer because the effect of preventing oxygen from permeating the magnetic layer is high. In order to reduce the distance between the magnetic layer and the head during recording and reproduction, the protective layer is preferably thin. Therefore 50 nm
Is preferably 30 nm or less, more preferably 20 nm or less. However, in order to obtain sufficient durability, the thickness is preferably 0.1 nm or more, more preferably 1 nm or more.

Further, it is preferable to form a lubricating layer on the protective layer. It has a function of preventing damage by a medium mask and a magnetic head. 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 can be applied by a conventional method such as a dip method or a spin coat method. The film may be formed by an evaporation method. In order not to hinder the formation of the magnetic pattern, the thickness of the lubricating layer is preferably thin, and is preferably 10 nm or less. More preferably, it is 4 nm or less. In order to obtain sufficient lubrication performance, the thickness is preferably 0.5 nm or more. More preferably, it is 1 nm or more. When the energy beam is irradiated from above the lubricating layer, re-application may be performed in consideration of the damage (decomposition, polymerization) of the lubricant. Further, other layers may be added to the above-mentioned layer constitution as needed.

In order not to impair the running stability of the flying / contact type head, the surface roughness R
a is preferably kept at 3 nm or less. The medium surface roughness Ra is the roughness of the medium surface not including the lubricating layer,
Stylus type surface roughness meter (Model name: Tencor P-12 disk profile
r (manufactured by KLA Tencor) with a measurement length of 400 μm and a value calculated according to JIS B0601.
More preferably, the thickness is 1.5 nm or less. Desirably, the surface waviness Wa of the medium after the formation of the magnetization pattern is kept at 5 nm or less. Wa is the waviness of the medium surface that does not include a lubricating layer, and is a stylus type surface roughness meter (model name: Tencor P-12 disk p
It is a value calculated according to Ra calculation after measuring with a measurement length of 2 mm using a rofiler (manufactured by KLA Tencor). More preferably, the thickness is 3 nm or less. Incidentally, the formation of the magnetization pattern on the magnetic disk thus configured is performed on the recording layer (magnetic layer). It is preferable to perform the method by any of the methods described after forming a protective layer, a lubricating layer, and the like on the recording layer, but may be performed immediately after the formation of the recording layer if there is no possibility of oxidation of the recording layer.

Various methods can be adopted as a film forming method for forming each layer of the magnetic disk. For example, physical vapor deposition such as direct current (magnetron) sputtering, high frequency (magnetron) sputtering, ECR sputtering, and vacuum vapor deposition is used. Law. As the conditions at the time of film formation, the ultimate vacuum, the substrate heating method and substrate temperature, the sputtering gas pressure, the bias voltage, and the like are appropriately determined according to the characteristics of the medium to be obtained. For example, in the case of sputtering film formation, the ultimate vacuum degree is usually 5 × 10 ⁻⁶ Torr.
Hereinafter, the substrate temperature is preferably from room temperature to 400 ° C., the sputtering gas pressure is preferably from 1 × 10 ^{−3 to} 20 × 10 ⁻³ Torr, and the bias voltage is preferably from 0 to −500 V.

When the substrate is heated, it may be heated before the formation of the underlayer. Alternatively, when a transparent substrate having a low heat absorption is used, the substrate is heated after forming a seed layer mainly composed of Cr or an underlayer having a B2 crystal structure in order to increase the heat absorption. After that, a recording layer or the like may be formed. When the recording layer is a rare-earth magnetic layer, the innermost and outermost parts of the disk are first masked to form a film up to the recording layer and then a protective layer from the viewpoint of corrosion and oxidation prevention. In this case, the mask is removed and the recording layer is completely covered with the protective layer. If the protective layer is composed of two layers, the film is formed with the recording layer and the first protective layer masked. It is preferable to remove the mask when forming the film, and to completely cover the recording layer with the second protective layer, because corrosion and oxidation of the rare earth magnetic layer can be prevented.

Next, the magnetic disk drive of the present invention will be described. A magnetic disk drive according to the present invention includes at least the magnetic disk described above, a drive unit for driving the magnetic disk in a recording direction, a magnetic head including a recording unit and a reproducing unit, and means for moving the magnetic head relative to the magnetic disk. When,
This is a magnetic disk device having a recording / reproducing signal processing means for performing signal input to the magnetic head and reproduction of an output signal from the magnetic head. More specifically, usually, a shaft for fixing one or more magnetic disks in a skewered manner, a motor for rotating a magnetic disk joined to the shaft via a bearing, and a magnetic head used for recording and / or reproduction And an arm to which the head is attached, and an actuator that can move the head to an arbitrary position on the magnetic recording medium via the head arm,
The recording / reproducing head moves over the magnetic recording medium at a constant flying height. The recording information is converted into a recording signal via a signal processing means and recorded by a magnetic head. Further, the reproduction signal read by the magnetic head is inversely converted through the signal processing means to obtain reproduction information.

On the magnetic disk, servo patterns composed of radially magnetized regions are formed at substantially equal angular intervals along concentric tracks. Information signals are recorded between the servo patterns in sector units. One sector is between two servo patterns. The magnetic disk drive of the present invention includes means for detecting and controlling the position of the magnetic head in the radial direction based on the servo pattern composed of the radial magnetization regions.

More specifically, the means can detect a magnetic flux in the direction perpendicular to the medium surface, which is generated by the magnetic head from the magnetic domain boundary of the radial magnetization area (orthogonal magnetization area), and can detect the polarity of the magnetic flux. To detect the radial position of the magnetic head
To control. At this time, in order to perform efficient servo pattern detection without loss, it is preferable that the radial width of the magnetic head be equal to or less than the radial average width of the unit pattern. The magnetic head reads a servo signal from the servo pattern, thereby accurately performing tracking at the center of the track, and reads an information signal of the sector.
At the time of recording, tracking is performed similarly, and information is recorded in the sector. According to the present invention, since the servo pattern is a radial magnetization pattern, high-accuracy tracking can be performed even with a small number of patterns, so that the track density of the magnetic disk can be increased. Further, the servo area can be narrowed, and the data recording area (information recording area) can be expanded accordingly. Therefore, according to the present invention,
The capacity of the magnetic disk device can be increased, or the size can be reduced with the same capacity. Various magnetic heads such as a thin film head, an MR head, a GMR head, and a TMR head can be used. In particular, by configuring the reproducing section of the magnetic head with an MR head, a GMR head, a TMR head, or the like, a sufficient signal intensity can be obtained even at a high recording density, and a magnetic disk device having a high recording density is realized. be able to.

The flying height of the magnetic head is set at 0.01.
When flying at a low height of not less than μm and less than 0.05 μm, the output is improved and a high device S / N is obtained, and a large capacity and highly reliable magnetic disk device can be provided.
Further, by combining a signal processing circuit based on the maximum likelihood decoding method, the recording density can be further improved.
A sufficient S / N can be obtained even when recording / reproducing at a recording density of at least kTPI, a linear recording density of 200 kFCI or more, and 2 Gbits per square inch or more. Further, when the flying height is less than 0.001 μm to less than 0.01 μm, for example,
Track density 13kTPI or more, linear recording density 250kF
A sufficient S / N can be obtained even when recording / reproducing at a recording density of CI or more and 3 Gbits / square inch or more.

Further, the reproducing portion of the magnetic head is disposed between 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 the conductive magnetic layers. G consisting of a conductive non-magnetic layer
MR head or G using spin valve effect
By using the MR head, the signal strength can be further increased, and 10 Gbits or more per square inch
A highly reliable magnetic recording device having a linear recording density of 50 kFCI or more can be realized.

[0059]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to the embodiments unless it exceeds the scope of the gist. Example 1 (Example in which at least a part of a magnetic domain boundary portion is displaced radially in steps) An example of the present invention will be described with reference to FIGS. 1 and 2. FIG.
(A) is a diagram schematically showing a part of the surface of a magnetic disk. Radial magnetized regions, which are servo patterns, are formed at substantially equal angular intervals, and an information magnetized pattern having circumferential magnetization is formed between them. The individual servo patterns are formed, for example, radially or radially as shown. Then, for example, several tens to several hundreds of such servo patterns are provided in one round. FIG. 2 (b)
FIG. 4 is an enlarged view of a part of the servo pattern area.
The magnetic disk is once uniformly magnetized toward the center of rotation by a strong external magnetic field (), and then irradiated with a laser beam in accordance with the pattern to be formed and locally heated while being locally heated. By applying a magnetic field, the pattern portion is magnetized in the outer peripheral direction, and a servo pattern is recorded (). FIG. 1 schematically shows the servo pattern area on the surface of the magnetic disk formed in this way and schematically shows the pattern portion. In the figure, N and S schematically show the perpendicular magnetization flowing at the magnetic domain boundary,
In N, upward magnetization is detected, and in S, downward magnetization is detected. The left and right sides of the figure are information recording directions (the direction in which tracks extend, the circumferential direction of the disk), and the upper and lower sides of the figure are orthogonal directions (radial directions of the disk). The lower side of the figure is the radial inner circumferential direction, and the upper side is the radial outer circumferential direction. The rotation center of the medium is below the figure, the medium moves leftward in the figure, and information is read from the left to the right by a magnetic head (not shown). An MR head is used for reading, and a high-frequency magnetic field change is detected with high sensitivity.

In FIG. 1, the central portion has a portion in which the magnetic domain boundary portion in the radial magnetization region (orthogonal magnetization portion) is displaced in a step shape in the radial direction. This can be formed by shaking the irradiation area of the laser light in the radial direction, but can also be formed by irradiating the laser light through a mask having a transmission portion having such a shape. The latter is preferable since a pattern can be formed easily in a short time. At the magnetic domain boundary of the orthogonal magnetization portion, an N pole appears at a portion where the magnetization is concentrated from the inner and outer circumferences, and an S pole appears at a portion where the magnetization is diffused toward the inner and outer circumferences. A pair of magnetic domain boundaries is always formed on the inner peripheral side and the outer peripheral side of the belt-shaped magnetization pattern extending in the recording direction, and the directions of the magnetic fields generated from both are opposite. That is, two position information signals of N and S can be obtained by writing one pattern. In order to detect such a signal efficiently without loss, it is preferable that the width in the radial direction of the detection head is equal to or smaller than the width of the average value of the magnetization unit pattern (unit pattern). Here, the magnetization unit pattern refers to each magnetic domain forming a servo pattern. In FIG. 1, the radial width of the detection head is preferably equal to or less than the radial width of the outer circumferential magnetic domain or the inner circumferential magnetic domain.

In order to obtain low noise and a high signal level, it is preferable that both the inner magnetic domain and the outer magnetic domain of the servo pattern are magnetized to a saturation state. In a conventional servo pattern written using a magnetic head, the write performance is reduced at the end of the head, and a non-magnetized portion is formed. On the other hand, in the disk of the present invention, magnetic portions are formed in all portions. And the occurrence of noise due to the non-magnetized portion is prevented.

Here, the unit pattern for servo shown in FIG. 1 is composed of two step portions which are shifted from each other by １ ／ of the repetition period in the radial direction of the unit pattern (１ ／ of the unit pattern width). Are arranged repeatedly in the radial direction at the same interval as the pattern width. That is, the repetition period of the unit pattern in the radial direction in FIG. 1 is twice as long as the unit pattern. This type of unit pattern is usually arranged at a period of 2 to 4 times the track pitch of the information recording track. For example, when there are recording tracks in I and III in FIG. 1, the unit patterns are arranged at a period twice as long as the track pitch of the recording tracks. FIG.
Also, when there are recording tracks in II and IV, the unit patterns are arranged with a period twice as long as the track pitch of the recording tracks. On the other hand, I, II, III, IV of FIG.
When all are recording tracks, the unit patterns are arranged at a period four times the track pitch of the recording tracks.

When a unit pattern is provided with a period twice as long as the track pitch, only one of the steps is used for position control. For example, when the step portion on the left side of the drawing is used, the information recording track is provided at the center line I of the unit pattern and at the position III where the center line coincides with the center line between the unit patterns.
When the magnetic head is located at the center of the information track I or III, the magnetic field generated by the N pole and the S pole generated on the side of the unit pattern is balanced, and no output is generated in the head. When the magnetic head moves in any radial direction, the action of one of the magnetic poles increases according to the size, and the head produces an output corresponding to the unit pattern.

In which direction the output corresponding to which pole is generated when shifting is determined by whether the center line of the information track matches the center of the unit pattern or the center line between the unit patterns. . Either of them can be detected by detecting the polarity of the step on the right side of the drawing. When the unit patterns are arranged at a cycle four times the track pitch, both the left and right steps may be used for control, and the steps not used for control may be used for code detection.

Servo patterns are provided at regular equal angular intervals in the data area, and in the servo pattern, this unit pattern is repeatedly recorded over a radial position range in which the head moves. Further, the magnetic field generated from the unit pattern is limited to a narrow range width near the magnetic domain boundary of the orthogonal magnetization portion, and this width is smaller than the repetition period of the unit pattern. Therefore, it is desirable to provide a plurality of the boundary portions in the unit pattern at different radial positions, and it is preferable to use a magnetic field generated by different portions of the same pattern for positioning adjacent tracks. In FIG.
Four boundary portions of N, N, S, and S are formed in one unit pattern.

The change in the radial position at the boundary of the orthogonal magnetization portion is as follows.
The simplest control becomes possible by providing in a step shape. It is preferable to set the step at a right angle because the relationship between the position deviation and the signal output is linear without causing a loss of recording space, and the control gain can be easily increased. However, it is strictly required due to the rounding of the laser beam and the pattern error of the mask. It is difficult to make a right angle. Actually, there are many cases where the steps are diagonal steps or curved steps as shown in FIG. The width of the step-like displacement is one of the repetition periods in the radial direction of the unit pattern.
It is preferably in the range of / 8 to 3/8. Thereby, signals having different phases can be obtained from one unit pattern. When the width of the step-like displacement is の of the repetition period of the unit pattern in the radial direction, the phase is completely opposite, and information having a different phase cannot be obtained. If the width of the step-like displacement is too small, the phase difference is small, and it is difficult to obtain a signal with high resolution. On the other hand, if it is too large, it becomes difficult to form such a sudden displacement magnetization pattern. More preferably, the width of the step-like displacement is 1/6, 1/1 of the repetition period of the unit pattern in the radial direction.
4 or 1/3. FIG. 1 shows an example of the case of 1/4. At this time, a so-called two-phase tracking signal is obtained, and up to four recording tracks can be provided in one unit pattern repetition period. On the other hand, 1 /
In the case of 6, 1/3, a so-called three-phase tracking signal is obtained, and up to six recording tracks can be provided in one unit pattern repetition period. The magnetic disk device according to the present invention can be obtained by incorporating the above magnetic disk into a magnetic disk device having a predetermined tracking circuit by incorporating an MR head.

Embodiment 2 (an example in which a magnetic domain boundary portion has a portion displaced in a substantially triangular wave shape with respect to the radius) Another embodiment of the present invention will be described with reference to FIG. FIG.
(A) is an enlarged view of a servo pattern area on the surface of a magnetic disk, schematically showing a pattern portion. In the figure, N and S schematically show the perpendicular magnetization that has flowed out at the boundary of the magnetic domain. In N, an upward magnetization is detected, and in S, a downward magnetization is detected. The left and right sides of the figure are information recording directions (the direction in which tracks extend, the circumferential direction of the disk), and the upper and lower sides of the figure are orthogonal directions (radial directions of the disk). The lower side of the figure is the radius inner circumference direction,
The upper side is the radial outer peripheral direction. The rotation center of the medium is below the figure, the medium moves leftward in the figure, and information is read from the left to the right by a magnetic head (not shown). An MR head is used for reading, and a high-frequency magnetic field change is detected with high sensitivity.

The medium is once magnetized uniformly in the direction of the center of rotation by a strong external magnetic field. Then, the medium is irradiated with a laser beam in accordance with the pattern to be formed and locally heated while being locally heated. , The pattern portion is magnetized in the outer peripheral direction. The orthogonal magnetization part as shown in FIG. 3A can be formed by irradiating a laser beam through a mask having a transmission part whose shape changes in accordance with a change in the radial position.

A thick line crossing FIG. 3 shows an example of reading by the head. A negative pulse is output in the S pole portion and a positive pulse is output in the N pole portion (see FIG. 3B). This servo pattern uses a unit pattern in which the radial position of the boundary between the orthogonal magnetization portions is changed linearly, and detects a phase difference. That is, the magnetic domain boundary portion of the orthogonal magnetization portion is formed obliquely and linearly with respect to the recording track.

This servo pattern is characterized in that the output pulse timing changes linearly as the radial position of the head changes. For example, when the head is moved along the head locus of FIG. 3A, four pulses as shown in FIG. 3B are obtained. When the head trajectory shifts toward the inner radius, the interval X between the first and second pulses becomes narrower, and when the head trajectory shifts toward the outer radius, the interval X between the first and second pulses increases. The radial position can be determined by measuring the time difference between the two pulses.

Further, it is possible to know on which inclined portion the head is located by the polarity of the pulse. To measure the timing, the time difference between the two pulses may be measured. For this purpose, as shown in FIG. 3, it is preferable that the magnetic domain boundary has a portion that is displaced in a substantially triangular wave shape with respect to the radius. Here, on one recording track, a pair of a magnetized boundary portion that is displaced linearly in a specific circumferential direction toward the outer periphery and a magnetized boundary portion that is displaced linearly in the opposite circumferential direction toward the outer periphery is paired. (For example, either pattern A or pattern B). As a result, it is possible to obtain two pulses in which the variation of the pulse timing due to the variation of the radial position of the head is in the opposite direction, and the radial position can be obtained by measuring the time difference between both pulses.
In FIG. 3, the top of the displacement of the magnetic domain boundary is rounded, and even if the head position is shifted in the radial direction, the interval between the third and fourth pulses does not change much. Not used for measurement. This is for the following reason.

First, the vertex portion of the displacement at the boundary portion has an infinite curvature, and it is difficult to accurately write this at the time of transfer or the like. In the magnetic transfer method and the optical transfer method, blurring generally occurs during transfer from a master, and it is difficult to transfer a fine pattern. Even if the data can be written, the magnetic field is disturbed in this portion, and the measurement accuracy is deteriorated. In order to avoid this, it is preferable to use a substantially triangular wave-like pattern having a rounded apex. The rounded portion is not used for measurement, and at a radial position crossing the rounded portion, the measurement is performed using another pattern end portion.

That is, in the example shown in FIG. 3, two patterns A and B are provided as servo patterns with inclined portions shifted in the radial direction, and when the head passes through the curved portion of one pattern, the other inclined portion is provided. Are configured to simultaneously pass through the center portion. The pulse interval is measured from each of the two patterns, but the measured value in which the interval is within a predetermined range is adopted, and the measured values indicating extremely long and short intervals are not used. The magnetic disk device according to the present invention can be obtained by incorporating the above magnetic disk into a magnetic disk device having a predetermined tracking circuit by incorporating an MR head.

As described above, according to the present invention,
By forming a coarse magnetization pattern that is easy to form, the head positioning servo of a high-density magnetic disk device can be performed accurately and easily, and as a result, a magnetic disk and a magnetic disk device capable of high-density recording are inexpensive. And it can be provided in a short time.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a magnetization pattern of a radial magnetization region according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a magnetization pattern according to the first embodiment.

FIG. 3 is an explanatory diagram of a magnetization pattern of a radial magnetization region according to another embodiment of the present invention.

FIG. 4 is an explanatory diagram of magnetization detection of the orthogonal magnetization unit according to the present invention.

[Explanation of symbols]

 1 Servo pattern (radial magnetization area) 2 Circumferential magnetization area

Claims (14)

[Claims] 1. A magnetic disk comprising at least one magnetic layer provided on a substrate, comprising: a magnetic domain having a magnetization direction of a radial direction and an inner circumferential direction; and a magnetic domain having a magnetization direction of a radial direction and an outer circumferential direction. A plurality of radially magnetized regions comprising magnetic domains are provided at substantially equal angular intervals. 2. The magnetic disk according to claim 1, wherein a circumferential magnetization region whose magnetization direction is a circumferential direction is provided between the adjacent radial magnetization regions. 3. A servo pattern for controlling the position of a recording / reproducing magnetic head or a reference pattern for recording a servo pattern, wherein the radial magnetization region is a reference pattern for recording a servo pattern.
A magnetic disk according to claim 1. 4. The magnetic disk according to claim 3, wherein the radial magnetization region has a portion in which a magnetic domain boundary between an inner circumferential magnetic domain and an outer circumferential magnetic domain is displaced in a radial direction. 5. The magnetic disk according to claim 4, wherein at least a part of the magnetic domain boundary portion is displaced radially in steps. 6. The magnetic disk according to claim 5, wherein the width of the step-like displacement is within a range of １ ／ to ／ of a radial repetition period of the unit pattern. 7. The magnetic disk according to claim 6, wherein the width of the step-like displacement is any one of 1/6, 1/4, and 1/3 of the radial repetition period of the unit pattern. 8. The magnetic disk according to claim 4, wherein the magnetic domain boundary portion has a portion that is displaced in a substantially triangular wave shape with respect to a radius. 9. A magnetic disk in which at least one magnetic layer is provided on a substrate, and a pattern provided on a mask is transferred by applying an external magnetic field, so that the magnetization direction is radial in the magnetic layer. A method for forming a magnetization pattern, comprising providing a magnetization pattern. 10. The magnetization according to claim 9, comprising: irradiating the disk with energy rays through a mask to locally heat the magnetic layer; and applying an external magnetic field to the magnetic layer. The method of forming the pattern. 11. A magnetic disk having a magnetization pattern formed by the method according to claim 9. Description: 12. A magnetic disk, a driving unit for driving the magnetic disk in a recording direction, a magnetic head comprising a recording unit and a reproducing unit, means for moving the magnetic head relative to the magnetic disk, and 12. A magnetic disk drive having recording / reproducing signal processing means for performing recording signal input and reproducing signal output from a magnetic head, wherein the magnetic disk is the magnetic disk according to claim 1. And a means for controlling a radial position of the magnetic head based on the magnetization pattern. 13. A magnetic flux in a direction perpendicular to a medium surface, which is generated from a magnetic domain boundary between an inner circumferential magnetic domain and an outer circumferential magnetic domain,
13. The magnetic disk drive according to claim 12, further comprising means for controlling a radial position of the magnetic head according to the polarity of the magnetic flux. 14. The magnetic disk drive according to claim 12, wherein the radial width of the magnetic head is equal to or less than the radial average width of the magnetization unit pattern.