JP3281292B2 - Magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus such as a hard disk drive, and more particularly to a high-density magnetic recording / reproducing apparatus using a perpendicular magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, with the rapid progress of the information society,
The amount of information handled is increasing rapidly. Along with this, the demand for higher density and higher capacity for information recording equipment such as magnetic recording / reproducing devices is not stopped. Among magnetic recording / reproducing devices, magnetic disk devices mainly used for computers, especially hard disk devices, have an annual rate of 30 to
The capacity is increased at a rate of 60%.

In a magnetic recording / reproducing apparatus such as a magnetic disk apparatus, as the recording density is increased, the medium area per recording bit is reduced, so that the S / N is reduced, and it becomes difficult to perform good reproduction with few errors. In order to solve this problem, there has been known a method of using an MR head utilizing a magnetoresistance effect as a reproducing head separately from a recording head. When an MR head is used as a reproducing head, in a magnetic recording medium, in order to increase the linear recording density, it is important to reduce the width of the magnetization reversal and simultaneously reduce the medium noise. In order to reduce medium noise and increase S / N for smaller recording bits, it is effective to reduce the minimum magnetization reversal unit on the medium and increase the number of magnetization reversal units included in the recording bit. It is.

On the other hand, as a method for increasing the linear recording density, 1
In 975, a perpendicular magnetic recording system was proposed. The perpendicular magnetic recording system is a perpendicular magnetic recording medium in which a recording layer has an easy axis of magnetization in a perpendicular direction, that is, a direction perpendicular to a film surface, as is well known,
In this method, recording is performed by using a so-called perpendicularly oriented medium to form magnetization in the recording layer in the vertical direction. In the perpendicular magnetic recording method, the demagnetizing field at the magnetization transition portion is smaller than that in the conventional longitudinal magnetic recording method in which recording is performed by forming magnetization in the longitudinal direction using a magnetic recording medium having in-plane anisotropy. Since it can be made extremely small and the magnetization transition width can be made narrower, higher density recording becomes possible.

In general, in a magnetic recording / reproducing apparatus for high-density recording, particularly in a hard disk drive, a magnetic head for recording / reproducing is correctly positioned on a target track, and the magnetic head follows the target track correctly. To this end, a method of magnetically recording a tracking servo signal on a medium in advance is used. There are various servo systems using such servo signals.A servo signal is recorded in advance for each sector obtained by dividing a track on a disk, and is read by a magnetic head to obtain relative position information between the head and the track. The obtained sector servo method is often used.

[0006] Although not limited to the sector servo system, the tracking servo signal is usually recorded / reproduced in order to simplify the processing by simplifying the servo processing circuit and to obtain a stable servo signal reproduction output. A lower frequency is used as compared with the data signal which is the original information to be obtained. Accordingly, the recording bit of the servo signal on the disk becomes low-density recording, so that it becomes magnetically stable in longitudinal magnetic recording.

[0007]

In magnetic recording media for high-density recording, the size of magnetic particles is generally reduced in order to form minute recording bits while maintaining a high S / N. If the size of the magnetic particles is too small, a thermal relaxation phenomenon occurs, and the spontaneous magnetization of the magnetic particles cannot be maintained in a fixed direction. As a result, there is a concern that the reproduced output may be attenuated due to thermal relaxation over time even if a magnetic pattern is formed on the magnetic recording medium such that a sufficient reproduced output can be obtained at the beginning of recording. Generally, when the anisotropy constant of the magnetic recording medium is Ku and the minimum unit volume of magnetization is v,
It is said that when Ku · v / kT <100, the effect of thermal relaxation appears. k is the Boltzmann constant and T is the absolute temperature.

In a normal longitudinal magnetic recording system, since a demagnetizing field in a recording bit is strong in a region where the recording density of a magnetic recording medium is high, since the magnetic particle diameter is relatively large,
There are reports that they are susceptible to this thermal relaxation.

On the other hand, in the perpendicular magnetic recording system, by growing the magnetic particles in the film thickness direction, the volume of the magnetic particles can be increased even if the particle size on the medium surface is equal to that in the longitudinal recording system. In addition, since it is magnetostatically stable even in a high-density recording area, it has attracted attention as a recording method which is less susceptible to thermal relaxation even with the same surface grain size as in the longitudinal magnetic recording method.

However, even in perpendicular magnetic recording, a certain limit is required for the film thickness in order to secure a sufficient recording magnetic field, and when a low-density recording area is present, on the contrary, it is larger than longitudinal recording. A demagnetizing field is generated in the recording bit, and is susceptible to thermal relaxation. For example, as described above, since a tracking servo signal is generally used at a low density because a lower frequency is used as compared with a data signal, perpendicular magnetic recording is susceptible to thermal relaxation, and the reproduction output of the servo signal is reduced. Decreases over time,
The reliability of the tracking servo decreases.

As a recording method for industrially utilizing a magnetic recording medium in which such a thermal relaxation phenomenon occurs, for example, a method of performing re-recording at regular time intervals has been proposed. Is difficult, and the problem of the effects of thermal relaxation cannot be avoided.

As described above, perpendicular magnetic recording has a higher recording resolution than longitudinal magnetic recording, and has the advantage that a large output can be obtained up to a high recording density. However, in particular, a servo signal for tracking recorded on a medium has a thermal effect. There is a problem that the reproduction output is reduced with the passage of time under the influence of the relaxation.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is possible to suppress a decrease in reproduction output due to thermal relaxation of a tracking servo signal in perpendicular magnetic recording, thereby enabling stable tracking servo for a long period of time. It is an object of the present invention to provide a magnetic recording / reproducing apparatus.

[0014]

In order to solve the above-mentioned problems, the present invention relates to a magnetic recording / reproducing apparatus using a perpendicular magnetic recording medium. Basically, the bit length is shortened to ensure the stability of the servo signal over time.

That is, the present invention provides a perpendicular magnetic recording medium having a recording layer on which a tracking servo signal is recorded,
In a magnetic recording / reproducing apparatus having at least one magnetic head for recording and reproducing information on and from this perpendicular magnetic recording medium, a maximum reduction in magnetization saturation in a recording bit where a servo signal of a recording layer is recorded is provided. The recording bit length (λ / 2) of the servo signal is set so that the magnetic field (Hdmax) is smaller than the coercive force (Hc) of the recording layer.

Further, the present invention more specifically defines the relationship between the magnetostatic characteristics of a perpendicular magnetic recording medium and the recording track width and recording wavelength (recording bit length) of a tracking servo signal, whereby Hdmax <Hc The thickness of the recording layer in the perpendicular magnetic recording medium is t, the coercive force is Hc, the saturation magnetization (saturation residual magnetization) is Ms, the recording track width of the servo signal is Tw, and When the recording bit length of the servo signal is λ / 2, the following relationship is satisfied.

[0017]

(Equation 7) Further, when the tracking servo signal is mainly composed of a continuous signal of the basic recording wavelength λ,

[0018]

(Equation 8) Or

[0019]

(Equation 9) Is satisfied. Equation (8) is for the case where the servo signal is approximated by a sine wave, and Equation (9) is for the case where the servo signal is approximated by a rectangular wave.

More preferably, the magnetic characteristics in the direction perpendicular to the film surface of the recording layer are such that after saturating the magnetization of the recording layer in the vertical direction, a magnetic field H1 represented by the following equation is applied in the same direction as the saturation magnetization. It is characterized in that the magnetization M1 at the time of addition satisfies a relationship within an error range of ± 5% with respect to the saturation magnetization Ms.

[0021]

(Equation 10)

In particular, when the servo signal is a continuous signal of the fundamental recording wavelength λ, the magnetic characteristics in the direction perpendicular to the film surface of the recording layer are obtained by saturating the magnetization of the recording layer in the perpendicular direction, It is characterized in that the magnetization M1 when the indicated magnetic field H1 is applied in the same direction as the saturation magnetization satisfies the relationship within an error range of ± 5% with respect to the saturation magnetization Ms.

[0023]

[Equation 11]

In particular, when the track width Tw is close to the recording wavelength λ, the magnetization of the recording layer is saturated in the vertical direction, and then a magnetic field H1 represented by the following equation is applied in the same direction as the saturation magnetization Ms. The magnetization M1 at the time satisfies a relationship within an error range of ± 5% with respect to the saturation magnetization Ms.

[0025]

(Equation 12)

Further, the perpendicular magnetic recording medium of the present invention has a squareness ratio of 1 when the magnetic properties in a direction perpendicular to the film surface of the recording layer are measured, and the tracking servo signal is magnetically recorded. Is desirable.

The perpendicular magnetic recording medium of the present invention is preferably a two-layer medium comprising a soft magnetic underlayer and a recording layer formed thereon. The tracking servo signal is recorded by a single pole type head or a ring type head.

According to the magnetic recording / reproducing apparatus of the present invention thus constituted, a temporal change due to thermal relaxation of the tracking servo signal recorded on the perpendicular magnetic recording medium is suppressed according to the principle described below.

FIG. 1 shows a state of a demagnetizing field in a recording bit in perpendicular magnetic recording. Assuming that the track width is Tw, the recording bit length is λ / 2, the thickness of the recording layer is t, and the magnitude of the magnetization Mz in the perpendicular direction of the recording layer is mz, the magnitude of the demagnetizing field Hd is expressed by the following equation. .

[0030]

(Equation 13)

The demagnetizing field Hd takes a maximum value Hdmax when the magnetization is saturated in the vertical direction (when mz = Ms). On the other hand, as typical magnetostatic characteristics of a magnetic recording medium,
FIG. 2 shows an example of the MH loop (magnetization curve). When the minimum magnetization reversal unit of the recording layer becomes smaller, the magnetization near the coercive force Hc decreases due to the thermal relaxation phenomenon, and Hc decreases when measured at a later time. In FIG. 2, the solid line indicates the initial M
The H loop is an MH loop after a certain period of time with a broken line.

The present inventors have investigated in detail the change with time of the magnetostatic property due to the thermal relaxation, and as a result, have measured M in a short time.
For the H loop, the region where dM / dH is large, that is, M
In a region where the curve of the H loop is steeply inclined, a change in the magnetization M after a lapse of time is drastic. In a region where the magnetization M is saturated (dM / dH = 0), the change with time of the magnetization M is the most. I found it small.

Therefore, even in the recording bit in which the tracking servo signal is recorded, if the magnetization M is saturated or close to it, the change over time of the magnetization M is small and the temporal stability of the servo signal is secured. Will be. Here, in the perpendicular magnetic recording medium, as described later, the maximum demagnetizing field Hdmax at the time of magnetization saturation in the recording bit is the coercive force Hdmax.
If it is smaller than c, the saturation state of the magnetization M is maintained. The maximum demagnetizing field Hdmax at the time of magnetization saturation in this bit becomes smaller as the recording bit length (λ / 2) becomes smaller. That is, by setting the recording bit length λ / 2 so that Hdmax <Hc according to the present invention, the temporal change of the servo signal can be reduced, and the initial object of the present invention is achieved.

FIG. 3A shows a typical example of an MH loop of a perpendicular magnetic recording medium. When measuring the magnetic properties in the direction perpendicular to the film surface of the recording layer (the normal direction of the film),
It is known that, since a shape demagnetizing field is generated in the film, an MH loop inclined with a straight line of H = 4πM as a whole is obtained as shown in FIG. For this reason, in a medium having a small Hc / 4πMs, the squareness ratio of the loop is low, and a change with time of the magnetization M due to thermal relaxation is remarkably observed in a wide region with respect to the applied magnetic field H. With respect to the magnetic characteristics measured for such a thin film, the original magnetic characteristics of the recording layer material in the absence of the shape demagnetizing field need to be corrected with a straight line of H = 4πM. At this time, the MH loop is as shown in FIG.

With respect to the intrinsic magnetic characteristics of the recording layer, a demagnetizing field Hd as shown in equation (13) is generated in a recording bit in which a signal such as a servo signal for tracking is recorded. Magnetization M with the in-bit demagnetizing field Hd applied
Is saturated, the magnetization M hardly changes with time, and conversely, the magnetization M changes greatly with time in a region where dM / dH is large. Therefore, if the magnetization M in the bit is saturated even when the demagnetizing field Hd is applied in the recording bit, that is, if dM / dH = 0, it is possible to reduce the temporal change of the reproduction output due to thermal relaxation. .

In the above description, the demagnetizing field Hd in the recording bit is calculated as the magnitude in one recording bit that exists alone. However, as shown in FIG.
When a continuous magnetization pattern is formed at (recording bit length λ / 2), the adjacent magnetization weakens the demagnetizing field Hd. When the magnetization is approximated to a sinusoidal continuous signal at a high recording density, if the track width Tw is infinite,
The magnitude of the demagnetizing field Hd 'in one recording bit is represented by the following equation.

[0037]

[Equation 14]

In this case, the track width Tw is set to an infinite length.
Is sufficiently large, the error of Hd 'in equation (14) is small, and as a result of computer analysis, the error of Hd' in equation (12) with respect to the actual demagnetizing field Hd is several% for λ · t / Tw <4. It is.

Further, in the case where the track width is greatly reduced with respect to the film thickness t in response to the trend of higher density in the future, the equation (12) assuming that the track width Tw is infinite is given by Will not fit. In this case, assuming that the servo signal to be recorded is a rectangular wave signal, that is, a binary signal having a recording bit length of λ / 2 (λ is a recording wavelength), a demagnetizing field Hd ″ at the bit center.
Is represented by the following equation.

[0040]

(Equation 15)

From the above, regarding the magnetic properties in the direction perpendicular to the film surface of the recording layer, after the magnetization of the recording layer is saturated in the perpendicular direction, the magnetic field H1 represented by the equation (10) is changed in the same direction as the saturation magnetization Ms. , The magnetization M1 is equal to the saturation magnetization Ms,
When dM / dH in this state is 0, the recording magnetization pattern is least affected by the thermal relaxation phenomenon.

When the recording magnetization pattern is a continuous signal of the recording wavelength λ, after saturating the magnetization of the recording layer in the vertical direction, the magnetic field H1 represented by the equation (11) is changed in the same direction as the saturation magnetization Ms. When the magnetization M1 when added is equal to the saturation magnetization Ms and dM / dH in this state is 0, the recording magnetization pattern is least affected by the thermal relaxation phenomenon.

When the track width Tw is close to the recording wavelength λ, the magnetization of the recording layer is saturated in the vertical direction,
When the magnetic field H1 represented by the equation (12) is applied in the same direction as the saturation magnetization Ms, the magnetization M1 is equal to the saturation magnetization Ms, and when dM / dH in this state is 0, the recording magnetization pattern is most likely to be heat. It is less susceptible to relaxation phenomena.

When the magnetic field H1 represented by the equations (10), (11), and (12) is applied in the same direction as the saturation magnetization Ms, the magnetization M1 must be completely equal to the saturation magnetization Ms as described above. However, if the error is within ± 5% of Ms, the degree to which the recorded magnetization pattern is affected by the thermal relaxation reduction can be reduced to a practically sufficient degree.

In the perpendicular magnetic recording medium, the orientation of the easy axis of magnetization in the perpendicular direction is easily aligned, and the original squareness ratio S and coercive force square of the recording layer material whose shape demagnetizing field is corrected as shown in FIG. The ratio S ^* is close to one. For this reason, approximately, if Hdmax <Hc, the magnetization M is saturated even if the maximum demagnetizing field Hdmax at the time of magnetization saturation is applied in the bit. From the above, for one recording bit,

[0046]

(Equation 16) Alternatively, for a continuous signal of the same recording wavelength,

[0047]

[Equation 17] By setting the recording bit length λ / 2 or the recording wavelength λ of the tracking servo signal so that the recording magnetization pattern satisfies the relationship, the fluctuation of the servo signal reproduction output over time due to the thermal relaxation phenomenon can be reduced.

In order to satisfy the condition of Hdmax <Hc for a perpendicular magnetic recording medium having a predetermined magnetic characteristic, the recording bit length λ / 2 is changed to change the maximum demagnetizing field H in the bit.
It is sufficient to keep dmax low. In other words, the recording bit length λ / 2 of the servo signal to be recorded is defined as shown in Expression (7) or the recording wavelength λ of the continuous servo signal is changed according to the magnetic characteristics of an arbitrary perpendicular magnetic recording medium. Equation (8)
May be specified as shown in FIG.

[0049]

Embodiments of the present invention will be described below. (First Embodiment) FIG. 5 shows a schematic configuration of a magnetic disk drive according to an embodiment of the present invention. The magnetic disk 1 is a perpendicular magnetic recording medium, and is driven to rotate by a spindle motor 2. On the other hand, a composite magnetic head 5 is attached to the tip of the rotary arm 4 driven by the voice coil motor 3.
Is installed. The composite magnetic head 5 is a head in which, for example, a single pole type head or a ring type head for perpendicular magnetic recording is used as a recording head, and an MR head (magnetoresistive type head) is used as a reproducing head, and is formed by thin film technology. You. A GMR head may be used as the MR head.

In the case of the sector servo system, for example, a tracking servo signal is recorded on the magnetic disk 1 as shown in FIG. That is, a track on the magnetic disk 1 is divided into a plurality of areas (referred to as sectors) in the circumferential direction, and some of these sectors are servo sectors, and others are data sectors. Are recorded in advance as tracking servo signals. A data signal is recorded in the data sector.

FIG. 7 shows a sectional view of an example of a perpendicular magnetic recording medium used as the magnetic disk 1. As shown in FIG. 1, the perpendicular magnetic recording medium has a structure in which a recording layer 12 and a protective film 13 are sequentially laminated on a rigid disk substrate 11.

FIG. 8 shows the M of such a perpendicular magnetic recording medium.
The measurement result of H loop (magnetization curve) is shown. Here, the thickness t of the recording layer 12 of the perpendicular magnetic recording medium is 25 [nm], K
u · v / kT = 80, coercive force Hc = 2900 [Oe],
The measurement was performed for 10 minutes using a sample vibration magnetometer (VSM) with the saturation magnetization Ms = 300 [emu / cc]. At points a, b, c, and d in the figure, the change in magnetization 48 hours after the application of the magnetic field is indicated by white circles. Although the attenuation of the magnetization is recognized at the points a and b, the points c and d in the saturation magnetization region
Then, almost no change in magnetization was recognized.

On this perpendicular magnetic recording medium, a tracking servo signal consisting of a continuous signal was recorded on-track, and the change over time in the reproduction output was examined. A ring-type head having a track width Tw of 1 μm was used for recording, and an MR head was used for reproduction. The change in reproduction output with time was as follows: the reproduction output immediately after recording (about 2 minutes later) was left at room temperature for half a year. The change in the reproduction output after the measurement was measured. The recording of a narrow track having a track width Tw of less than 1 μm was performed by recording a signal with a 1 μm track width, then off-tracking the head position, and erasing a part of the recording track.

Table 1 shows the results obtained by measuring the track width Tw, the magnitude relationship between the coercive force Hc and the demagnetizing field Hd, and the reproduction output with time for each recording bit length (recording density). Here, with respect to the change with time in the reproduction output, those having an attenuation of 15% or more during the lapse of half a year are indicated by "x", and those whose attenuation is less than 15% are indicated by "o" (the same applies hereinafter).

[0055]

[Table 1]

As is apparent from the results, the coercive force Hc
And the maximum demagnetizing field Hdmax in the bit is Hd <H according to the present invention.
When the relationship of c is satisfied, the reproduction output change with time is reduced.

Next, as a comparative example, the same measurement was performed using a longitudinal magnetic recording medium, and the results are shown in Table 2. The coercive force of the medium used here is Hc = 2200 [Oe], Ku · v /
kT = 65.

[0058]

[Table 2]

As described above, in the longitudinal magnetic recording, as the recording density increases, the reproduction output changes with time, as opposed to the perpendicular magnetic recording. In longitudinal magnetic recording, the smaller the recording bit, the stronger the demagnetizing field inside the medium.

(Second Embodiment) Next, an example in which a medium having magnetic characteristics different from those of the first embodiment is used as a perpendicular magnetic recording medium will be described. The maximum demagnetizing field Hdmax at the time of magnetization saturation in the recording bit of the recording layer in the perpendicular magnetic recording medium,
Ie

[0061]

(Equation 18) Does not exceed 4πMs, so always

[0062]

[Equation 19] It is.

Therefore, in a medium having a squareness ratio of 1 when the magnetic characteristics in the direction perpendicular to the film surface of the recording layer including the shape demagnetizing field are 1, an arbitrary track width Tw of the servo signal is obtained.
Unconditionally, for the recording wavelength λ, “the magnetization M1 when the magnetic field H1 is applied in the same direction as the saturation magnetization after the magnetization of the recording layer is saturated in the vertical direction is equal to the saturation magnetization Ms”.
It satisfies the relationship.

However, it is difficult to define that the two values of M1 and Ms are equal in terms of the magnetic characteristics, because the measurement actually includes the measurement error of the magnetization. Therefore, a certain track width Tw
And the difference between the magnetization value M1 and the saturation magnetization Ms when the magnetic field H1 determined by the recording wavelength λ is applied (including the measurement error) (Ms−M
Table 3 shows the results of measuring the change over time of the reproduced signal output with respect to 1) / Ms after half a year.

[0065]

[Table 3]

From this result, it can be seen that when the difference between M1 and Ms is within 5%, the reproduction output has little change with time. Further, Table 4 shows the measurement results of the change over time in the reproduction output according to the magnetic characteristics of the perpendicular magnetic recording medium. In this example, the film thickness t, Ku · v / kT, coercive force Hc, saturation magnetization Ms, track width Tw, and recording bit length λ / 2 are changed to change the magnitude relationship between the coercive force Hc and the demagnetizing field Hd and the reproduction output time. The change is being measured.

[0067]

[Table 4]

As is clear from these results, the coercive force Hc and the maximum demagnetizing field Hdmax at the time of magnetization saturation in the bit are Hdmax <Hc according to the present invention in any magnetic characteristics.
When the relationship is satisfied, it can be understood that the temporal change in the reproduction output is reduced.

In the perpendicular magnetic recording medium shown in FIG. 7, the recording layer 12 was formed directly on the substrate 11, but the soft magnetic layer was first formed on the substrate, and the recording layer was formed thereon. The present invention can be similarly applied to a case where a medium is used.

[0070]

As described above, according to the present invention, it is possible to reduce the influence of thermal relaxation on a tracking servo signal recorded on a perpendicular magnetic recording medium and obtain a stable servo signal reproduction output for a long time. Becomes possible.

In the present invention, as a secondary effect of forming a servo signal at a higher recording density than before, the area occupied by the servo signal area on the medium is reduced, and the data recording efficiency of the magnetic disk is improved. There is also the advantage of doing so.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a demagnetizing field generated in a recording bit.

FIG. 2 is a diagram showing a typical example of an MH loop of a magnetic recording medium.

FIG. 3 is a diagram illustrating an MH loop in a state where a shape demagnetizing field is applied to a perpendicular magnetic recording medium and in a state where demagnetizing field correction is performed;

FIG. 4 is an explanatory diagram of a demagnetizing field generated in a continuous magnetization pattern.

FIG. 5 is a schematic configuration diagram of a magnetic disk drive according to the present invention.

FIG. 6 is a diagram showing an example of a servo pattern on a magnetic disk by a sector servo method.

FIG. 7 is a sectional view showing a configuration of a perpendicular magnetic recording medium.

FIG. 8 is a diagram showing a measurement result of an MH loop of a perpendicular magnetic recording medium and its temporal change.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magnetic disk (perpendicular magnetic recording medium) 2 ... Spindle motor 3 ... Voice coil motor 4 ... Rotating arm 5 ... Composite magnetic head 11 ... Disk substrate 12 ... Recording layer 13 ... Protective layer

Claims (11)

(57) [Claims] 1. A magnetic recording apparatus comprising: a perpendicular magnetic recording medium having a recording layer on which a tracking servo signal is recorded; and at least one magnetic head for recording and reproducing information on and from the perpendicular magnetic recording medium. In the reproducing apparatus, the recording bit length of the servo signal is set so that the maximum demagnetizing field at the time of magnetization saturation in the recording bit of the recording layer where the servo signal is recorded is smaller than the coercive force of the recording layer. Characteristic magnetic recording / reproducing device. 2. A magnetic recording apparatus comprising: a perpendicular magnetic recording medium having a recording layer on which a tracking servo signal is recorded; and at least one magnetic head for recording and reproducing information on and from the perpendicular magnetic recording medium. In the reproducing apparatus, the thickness of the recording layer is t, the coercive force is Hc, and the saturation magnetization is Ms.
When the recording track width of the servo signal is Tw and the recording bit length is λ / 2, A magnetic recording / reproducing apparatus, characterized by satisfying the following relationship: 3. A magnetic recording apparatus comprising: a perpendicular magnetic recording medium having a recording layer on which a servo signal for tracking is recorded; and at least one magnetic head for recording and reproducing information on and from the perpendicular magnetic recording medium. In the reproducing apparatus, the thickness of the recording layer is t, the coercive force is Hc, and the saturation magnetization is Ms.
When the recording track width of the servo signal is Tw, and the servo signal is mainly composed of a continuous signal of the basic recording wavelength λ, A magnetic recording / reproducing apparatus, characterized by satisfying the following relationship: 4. A magnetic recording apparatus comprising: a perpendicular magnetic recording medium having a recording layer on which a servo signal for tracking is recorded; and at least one magnetic head for recording and reproducing information on and from the perpendicular magnetic recording medium. In the reproducing apparatus, the thickness of the recording layer is t, the coercive force is Hc, and the saturation magnetization is Ms.
When the recording track width of the servo signal is Tw, and the servo signal is mainly composed of a continuous signal of the basic recording wavelength λ, A magnetic recording / reproducing apparatus, characterized by satisfying the following relationship: 5. The magnetic characteristics of the recording layer in the direction perpendicular to the film surface are obtained by saturating the magnetization of the recording layer in the perpendicular direction. 3. The magnetic recording / reproducing apparatus according to claim 2, wherein the magnetization M1 when the magnetic field H1 represented by the following expression is applied in the same direction as the saturation magnetization satisfies a relationship within an error range of ± 5% with respect to the saturation magnetization Ms. apparatus. 6. The magnetic properties of the recording layer in the direction perpendicular to the film surface are obtained by saturating the magnetization of the recording layer in the perpendicular direction. 5. The magnetic recording according to claim 4, wherein when the magnetic field H1 represented by the following expression is applied in the same direction as the saturation magnetization Ms, the magnetization M1 satisfies a relationship within ± 5% of the saturation magnetization Ms. Playback device. 7. The magnetic characteristics of the recording layer in the direction perpendicular to the film surface are obtained by saturating the magnetization of the recording layer in the perpendicular direction. 4. The magnetic recording according to claim 3, wherein when the magnetic field H1 represented by the following expression is applied in the same direction as the saturation magnetization Ms, the magnetization M1 satisfies a relationship within ± 5% of the saturation magnetization Ms. Playback device. 8. The perpendicular magnetic recording medium has a squareness ratio of 1 when a magnetic characteristic in a direction perpendicular to a film surface of the recording layer is measured.
8. The magnetic recording / reproducing apparatus according to claim 1, wherein the tracking servo signal is magnetically recorded on the recording layer. 9. The magnetic recording / reproducing apparatus according to claim 1, wherein the perpendicular magnetic recording medium comprises a soft magnetic underlayer and a recording layer formed thereon. 10. The apparatus according to claim 1, wherein said tracking servo signal is recorded by a single pole type head.
10. The magnetic recording and reproducing apparatus according to any one of claims 9 to 9. 11. The apparatus according to claim 1, wherein said tracking servo signal is recorded by a ring type head.
10. The magnetic recording and reproducing apparatus according to any one of claims 9 to 9.