Magnetic recording and reproducing apparatus and control method thereof, magnetic recording medium, and stamper for manufacturing of magnetic recording medium

A magnetic recording and reproducing apparatus has a magnetic recording medium onto which servo information including position information is recorded by a concavo-convex pattern formed by a magnetic layer and a signal processing circuit that generates position control signal of a magnetic head based on amplitude values of fundamental wave component and at least one harmonic component in a reproduced signal of the position information. This magnetic recording and reproducing apparatus can increase the output of the position control signal and also increase the accuracy of the positioning control of the magnetic head.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic recording and reproducing apparatus including a magnetic recording medium such as a discrete track medium or patterned medium and a control method thereof, a magnetic recording medium, and a stamper for manufacturing of a magnetic recording medium.

2. Description of the Related Art

A magnetic recording and reproducing apparatus including a magnetic recording medium on which positioning information used for positioning control for a magnetic head is recorded has been conventionally known.

FIG. 17shows an exemplary magnetic recording medium included in the conventionally known magnetic recording and reproducing apparatus.

The magnetic recording medium100shown inFIG. 17has a plurality of servo region102radially formed at predetermined intervals. A concavo-convex pattern formed by a magnetic layer forms each servo region102.

Servo information is stored in the servo region102. As shown inFIG. 18that shows the servo region102in an enlarged state, the servo information includes a preamble portion104, a servo mark portion106, an address portion108in which address information is stored, and a burst portion110in which position information is stored. User data is to be recorded on data tracks112as shown in the same figure.

A burst pattern formed by four types of burst signal groups110A,110B,110C, and110D is formed as the position information in the burst portion110of the servo region102. The burst signal groups110A and110B are arranged as a pair of position information in such a manner that they each symmetrically extend with respect to the center line of the corresponding data track112. The burst signal groups110C and110D are arranged as another pair of position information at positions shifted from the burst signal groups110A and110B by a half of a track pitch, respectively.

FIG. 19is an enlarged view of the burst signal group110A. The other burst signal groups110B,110C, and110D also have the same structure as that of the burst signal group110A.

As shown inFIG. 19, the burst signal group110A (110B,110C, or110D) is formed by a plurality of (about 10 to 30 in a typical case) concavo-convex patterns arranged in a circumferential direction. In the concavo-convex pattern, convex portions (mesh portions inFIG. 19) formed by a magnetic layer (magnetic material) have a length BL1in the circumferential direction and a radial width BW1in a radial direction, and concave portion have a length BL2in the circumferential direction. In general, the magnetic recording and reproducing apparatus rotates the magnetic recording medium100at a constant angular velocity. Thus, the circumferential length BL1of the convex portion and the circumferential length BL2of the concave portion are varied depending on their positions in the radial direction on the magnetic recording medium100, and they become longer from an inner circumferential side to an outer circumferential side of the magnetic recording medium100.

The burst pattern in the burst portion110is formed by arranging each burst signal group (110A,110B,110C, or110D) at a plurality of positions at an interval BW2in the radial direction, as shown inFIG. 20.

A position control circuit124reproduces the above burst pattern. An exemplary position control circuit124is shown inFIG. 21. This position control circuit124is composed of an amplifier116that amplifies reproduced signal read by a magnetic head114, a signal processing circuit118(that comprises an LPF (Low Pass Filter)118A, an HPF (High Pass Filter)118B, and an amplitude detector118C), a sample hold unit120that holds position control signal after signal processing, and a differential amplification circuit122.

After the burst pattern recorded on the magnetic recording medium100is read by the magnetic head114, the reproduced signal of the burst pattern is amplified by the amplifier116and is then input to the signal processing circuit118. The reproduced signal input into the signal processing circuit118is output to the sample hold unit120as position control signal after only the fundamental wave component of the reproduced signal is extracted. The sample hold unit120holds the position control signals of the burst signal groups110A,110B,110C, and110D. The differential amplifier122obtains an output difference between the position control signals of the burst signal groups110A and110B or between the position control signals of the burst signal groups110C and110D, thereby acquiring position information of the magnetic head114. In this manner, positioning (tracking) control for the magnetic head114is carried out (refer to Japanese Patent Laid-Open Publication No. Hei 7-78432 for example).

However, in case of a magnetic recording medium such as a discrete track medium and a patterned medium, on which the burst pattern (position information) is recorded by the concavo-convex pattern formed by the magnetic layer, a magnetization signal of the concavo-convex pattern is recorded with unidirectional polarity. Thus, the reproduced signal of the concavo-convex pattern has a waveform shown inFIG. 22. InFIG. 22, mesh portions represent a plan view of the convex portions in the concavo-convex pattern. Please note that the reproduced signal waveform of the concavo-convex pattern inFIG. 22is an example in the case where the magnetic layer is a perpendicular magnetic recording layer.

In that magnetic recording medium in which the burst pattern is recorded by the concavo-convex pattern formed by the magnetic layer, the output level of the position control signal used for positioning control for the magnetic head is about half, as compared with a conventional continuous-layer medium in which a magnetization signal of a concavo-convex pattern is recorded with bidirectional polarity. Thus, improvement of the position control for the magnetic head has a limitation.

SUMMARY OF THE INVENTION

In view of the foregoing problems, various exemplary embodiments of this invention provide a magnetic recording and reproducing apparatus and a control method thereof that can make an output of a position control signal larger and can perform positioning control for a magnetic head with high precision as well as a magnetic recording medium used therefor and a stamper for manufacturing of a magnetic recording medium used to manufacture this magnetic recording medium.

The inventors of the present invention focused on the fact that reproduced signal of position information was comparatively close to sine waves on a conventional continuous-layer recording medium with reduced harmonic components included therein, and that in contrast reproduced signal waveforms of discrete track media and patterned media which only have magnetization signal with a single-direction polarity are different from sine waves as well as ever increasing harmonic components included in the reproduced signal. As a result, the inventors of the present invention discovered that position control signal can be increased by adding harmonic component to fundamental wave component of reproduced signal of position information.

Accordingly, various exemplary embodiments of the present invention provide a magnetic recording and reproducing apparatus comprising: a magnetic recording medium onto which servo information including position information is recorded by a concavo-convex pattern formed by a magnetic layer,; and

signal processing device that generates a position control signal of a magnetic head based on amplitude values of fundamental wave component and at least one harmonic component in a reproduced signal of the position information.

More over various exemplary embodiments of the present invention provide

a control method of a magnetic recording and reproducing apparatus comprising performing position control of a magnetic head based on amplitude values of fundamental wave component and at least one harmonic component in a reproduced signal of position information recorded on a magnetic recording medium by a concavo-convex pattern formed by a magnetic layer.

Furthermore, various exemplary embodiments of the present invention provide

a magnetic recording medium on which position information is recorded, the position information comprising burst signal groups wherein a plurality of the concavo-convex patterns are arranged in a circumferential direction, and wherein a concavo-convex ratio A/B between a length A in the circumferential direction of a concave portion and a length B in the circumferential direction of the convex portion on the identical burst signal groups is within a range of larger than 0.19 and smaller than 1.

Various exemplary embodiments of the present invention provide

a stamper for manufacturing of a magnetic recording medium wherein a concavo-convex pattern is formed to have a convex portion that corresponds to the concave portion of the concavo-convex pattern on the magnetic recording medium and a concave portion that corresponds to the convex portion of the concavo-convex pattern on the magnetic recording medium.

The term “position information” in this application shall refer to information used for positioning (tracking) control for a magnetic head. A burst pattern recorded on a burst portion of a servo region corresponds to the “position information.”

The term “reproduced signal of position information” in the present invention shall refer to a signal output when a magnetization signal of the concavo-convex pattern is reproduced by means of the magnetic head, as well as a signal obtained by amplifying that signal.

The magnetic recording and reproducing apparatus and the control method thereof according to the present invention have an excellent effects that the output of the position control signal can be made larger and the positioning control for the magnetic head can be performed with high precision.

The magnetic recording medium according to the present invention has an excellent effect of making it possible to provide a magnetic recording and reproducing apparatus that the output of the position control signal can be made larger and the positioning control for the magnetic head can be performed with high precision.

The stamper for manufacturing of a magnetic recording medium according to the present invention has an excellent effect of making it possible to manufacture a magnetic recording medium used in a magnetic recording and reproducing apparatus that the output of the position control signal can be made larger and the positioning control for the magnetic head can be performed with high precision.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, a magnetic recording and reproducing apparatus and a control method thereof according to first to third exemplary embodiments of the present invention will be described with reference to the drawings.

The magnetic recording and reproducing apparatus (not shown) of the first exemplary embodiment includes a magnetic recording medium2having a disk-like shape, as shown inFIG. 1. A plurality of servo region4and a plurality of user data region6are alternately arranged in a circumferential direction on the magnetic recording medium2.

Servo information is stored in the servo region4. As shown inFIG. 2, the servo information includes a preamble portion104, a servo mark portion106, an address portion108in which address information is stored, and a burst portion110in which position information is stored. A burst pattern (position information) that is formed by arranging each burst signal group110A (110B,110C, or110D) at a plurality of positions in a radial direction is formed in the burst portion110. User data is to be stored in data tracks112as shown in the figure.

FIG. 3is a view showing a part of the burst pattern (one type of burst signal group in this exemplary embodiment) formed in the servo region4of the magnetic recording medium2, and corresponds toFIG. 20described above.

A structure of a concavo-convex pattern in the burst pattern of the magnetic recording medium2and arrangement of burst signal groups are the same as those of the aforementioned conventional magnetic recording medium100. For the conventional magnetic recording medium100however, the concavo-convex ratio BL2/BL1between the length BL2of the concave portion in the circumferential direction and the length BL1of the convex portion in the circumferential direction on an identical burst signal group is 1. In contrast to this fact, the concavo-convex ratio BL2/BL1on an identical burst signal group for the magnetic recording medium2is formed to be in a range of larger than 0.19 and smaller than 1. The concavo-convex pattern can be formed by providing convex portions152formed by a magnetic layer on a substrate150that is formed by a glass substrate, an underlayer, a soft magnetic layer, a seed layer, and the like, as shown inFIG. 4. Concave portions154may be filled with a filling material formed of SiO2and the like.

On the other hand, a plurality of recording tracks arranged in an approximately concentric pattern are formed in the user data region6. The recording track is formed by convex portions of a concavo-convex pattern. The recording tracks are magnetically separated from each other by a plurality of grooves concentrically formed by concave portions of the concavo-convex pattern. User data is stored as magnetization information in the user data region6.

The concavo-convex pattern of this magnetic recording medium2is formed (recorded) on the magnetic recording medium2following the procedure described below using a stamper30for manufacturing of a magnetic recording medium as shown inFIG. 5A. Incidentally, a concavo-convex pattern complementary to that of the magnetic recording medium2is formed in advance on the stamper30for manufacturing of a magnetic recording medium. The convex portions of the stamper30for manufacturing of a magnetic recording medium are arranged to correspond to the concave portions of the magnetic recording medium2and the concave portions of the stamper30for manufacturing of a magnetic recording medium are arranged to correspond to the convex portions of the magnetic recording medium2.

At first, a starting body of an object to be processed32is prepared, as shown inFIG. 5A. As an example, the starting body of the object to be processed32can be acquired by depositing an underlayer, a soft magnetic layer, a seed layer, a continuous recording layer, and a mask layer over a glass substrate by sputtering in this order to form a plate shaped body32A and then using a spin coating method to further coat a resist layer32B onto the plate shaped body32A.

Next, as shown inFIG. 5B, using the stamper30for manufacturing of a magnetic recording medium, the concavo-convex pattern is formed on the resist layer32B of the starting body of the object to be processed32by, for example, a nano-imprinting technique. The resist layer32B of the bottom portion of the concave portion is removed and then the mask layer and the continuous recording layer of the plate shaped body32A are removed by etching, for example, to create the concavo-convex pattern on the plate shaped body32A as shown inFIG. 5C. Incidentally, the concave portions of the concavo-convex pattern may be filled with a filler material of, for example, SiO2.

The burst pattern on the magnetic recording medium2is reproduced by means of the magnetic recording and reproducing apparatus as described below.

FIG. 6is a block diagram of a position control circuit10of the magnetic recording and reproducing apparatus (not shown) of the first exemplary embodiment, and corresponds to the conventional position control circuit124shown inFIG. 21described above. The structure of the magnetic recording and reproducing apparatus according to the first exemplary embodiment is identical to the above-mentioned conventional magnetic recording and reproducing apparatus except for the magnetic recording medium2and the position control circuit10. Consequently, identical reference numerals in the figures are assigned for identical parts and their descriptions will be omitted (same situation applies to exemplary embodiments below).

The position control circuit10that is one of features of this first exemplary embodiment will now be described in detail.

As shown inFIG. 6, the position control circuit10is equipped with a signal processing circuit12in place of the signal processing circuit118in the conventional position control circuit124.

The signal processing circuit12comprises signal extractors (signal extraction devices)14and16that extract each signal of fundamental wave component and second order harmonic component from reproduced signal of position information recorded on the magnetic recording medium, amplitude detectors (amplitude detection devices)18and20that detect the amplitude values of the respective signals, and an adder (signal adding device)22that adds the amplitude values of the respective signals for generation of position control signals.

The signal extractor14is composed of an LPF14A that removes frequency components at regions higher than the fundamental wave component of the reproduced signal and an HPF14B that removes frequency components at regions lower than the fundamental wave component of the reproduced signal. Only the signal of the fundamental wave component is extracted from the reproduced signal. On the other hand, the signal extractor16is composed of an LPF16A that removes frequency components at regions higher than the second order harmonic component of the reproduced signal and an HPF16B that removes frequency components at regions lower than the second order harmonic component of the reproduced signal. Only the signal of the second order harmonic component is extracted from the reproduced signal.

The amplitude detector18detects amplitude values of signal of fundamental wave component extracted by the signal extractor14. On the other hand, the amplitude detector20detects the amplitude values of the signal of the second order harmonic component extracted by the signal extractor16.

The adder22adds the amplitude values of the signal of the fundamental wave component and the amplitude values of the signal of the second order harmonic component detected by the respective amplitude detectors18and20. The adder22then generates position control signal used for positioning control of the magnetic head114.

Next, the operation of the magnetic recording and reproducing apparatus according to the first exemplary embodiment will be described.

A reproduced signal of position information read by the magnetic head114is amplified by the amplifier116and is then input to the signal processing circuit12. After only the fundamental wave component and the second order harmonic component of the reproduced signal input into the signal processing circuit12are extracted, the amplitude value of the signal of the fundamental wave component and the amplitude value of the signal of the second order harmonic component are added and then output to the sample hold unit120as position control signal. The sample hold unit120holds the position control signal of the burst signal groups110A,110B,110C, and110D. The differential amplifier122obtains an output difference between the position control signals of the burst signal groups110A and110B or between the position control signals of the burst signal groups110C and110D, thereby acquiring information on the position of the magnetic head114. In this manner, positioning (tracking) control for the magnetic head114is performed.

The magnetic recording and reproducing apparatus according to the first exemplary embodiment has a magnetic recording medium onto which servo information including position information is recorded by a concavo-convex pattern formed by a magnetic layer and signal processing device (the signal processing circuit12in the first exemplary embodiment) that generates position control signal of the magnetic head114based on amplitude values of the fundamental wave component and at least one harmonic component in the reproduced signal of the position information. Therefore, the output of the position control signal can be made larger and positioning control can be performed with high precision.

Furthermore, the control method of the magnetic recording and reproducing apparatus according to the first exemplary embodiment performs positioning control of the magnetic head114based on amplitude values of the fundamental wave component and at least one harmonic component in the reproduced signal of the position information recorded on a magnetic recording medium by a concavo-convex pattern formed by a magnetic layer. It is possible to make the output of the position control signal larger and perform positioning control with high precision.

The signal processing device comprises signal extraction devices (the signal extractors14and16in the first exemplary embodiment) which extract the fundamental wave component and at least one harmonic component from the reproduced signal of the position information, amplitude detection devices (the amplitude detectors18and20in the first exemplary embodiment) which detect the amplitude values of the respective signals, and signal adding device (the adder22in the first exemplary embodiment) that adds the amplitude values of the respective signals and generates position control signal. Because of this, it is possible to eliminate noise contained in the frequency components except for the fundamental wave component and harmonic component of the reproduced signal to stabilize the position control signal.

Furthermore, because the harmonic component contains a second order harmonic component, the output of the position control signal can be effectively increased.

Even further, because the harmonic component only consists of the second order harmonic component, the effects of noise due to harmonic component can be suppressed and the position control signal stabilized.

The inventors of the present invention used the magnetic recording and reproducing apparatus according to the first exemplary embodiment and measured output values of position control signal. As a comparative example, the output values (amplitude values) of the fundamental wave components (conventional position control signal) of reproduced signals of burst patterns when using a conventional position control circuit were measured.

Table 1 shows these measurement results.

As shown in Table 1, in this experiment a plurality of data were taken for various burst patterns of which the length BL1of the convex portion in the circumferential direction and the length BL2of the concave portion in the circumferential direction vary. In Table 1, the value of the length of the convex portion in the circumferential direction and the value of the length of the concave portion in the circumferential direction of the burst patterns each show a value of length in the circumferential direction of the concave portion and a value of length in the circumferential direction of the convex portion of an identical burst signal group at a position with a radius of 20 mm on a 2.5-inch disk. In addition, the width BW1in the radial direction of the convex portion and the width BW2in the radial direction of the concave portion of the burst patterns were both 200 nm. Moreover, the track pitch of the data tracks was set to 200 nm (127 kTPI) and the width of the data track was set to 120 nm.

A perpendicular magnetic recording layer having a thickness of 15 nm was formed as the recording layer. This perpendicular magnetic recording layer formed the convex portions of the burst pattern shown inFIG. 3, and was magnetized to generate a magnetic field of a servo signal. More specifically, magnetic poles of an electromagnet that generates a direct-current field of 1.2×106A/m were arranged in such a manner that a disk surface was parallel to surfaces of the magnetic poles. Then, servo information was recorded by providing magnetization to the perpendicular magnetic recording layer in the servo region in the lump. When the magnetic characteristics of the perpendicular magnetic recording layer were measured by means of a vibrating sample magnetometer (VSM), saturated magnetization Bs was 0.44 T and residual saturated magnetization Br was 0.43 T.

While the magnetic recording medium having the above structure was rotated at 4200 rpm, the magnetic head was flown above a position corresponding to 20 mm in radius on the 2.5-inch disk at a height of 11 nm. In this state, the burst pattern was reproduced by a GMR magnetic head having a reading width of 120 nm and the output of the position control signal was measured for each of the magnetic recording and reproducing apparatus of the first exemplary embodiment and the conventional magnetic recording and reproducing apparatus. In Table 1 shown above, the output value of the fundamental wave component was standardized so as to be 1.00 when the concavo-convex ratio A/B between the length A in the circumferential direction of the concave portion and the length B in the circumferential direction of the convex portion was 1.00.

FIG. 7shows a graph of the relationship between the concavo-convex ratio of the burst pattern and the standardized output values based on the measurement results in Table 1. The solid line in the figure indicates the output value of the position control signal of the first exemplary embodiment and the broken line indicates the output value of the position control signal of the comparative example.

As shown in Table 1 andFIG. 7, it was understood that in the magnetic recording and reproducing apparatus according to the first exemplary embodiment, the output values of the position control signals were identical or become larger compared to the comparative example when the concavo-convex ratios were within a range of larger than 0.14 and smaller than 0.19 as well as within a range of larger than 1.00 and smaller than 3.00. Furthermore, it was discovered that the output values of the position control signals could be greatly increased compared to other concavo-convex ratios when the concavo-convex ratios were within a range of larger than 0.19 and smaller than 1.00. In other words, the magnetic recording and reproducing apparatus according to the first exemplary embodiment can increase the output of the position control signal because the concavo-convex ratio BL2/BL1between the length BL2in the circumferential direction of the concave portion and the length BL1in the circumferential direction of the convex portion in the identical burst signal group is within a range of larger than 0.19 and smaller than 1.

The output values of the position control signals had tendency to decrease when the concavo-convex ratios were in a range less than 0.5. This is thought to be due to the fact that third order, or higher, harmonic components become larger.

The inventors of the present invention further measured a position error signal (PES) with respect to the magnetic head position for each of the magnetic recording and reproducing apparatus of the first exemplary embodiment and the conventional magnetic recording and reproducing apparatus.

In the magnetic recording and reproducing apparatus according to the first exemplary embodiment, position error signals were measured when the length in the circumferential direction of the convex portion of the burst pattern was 250 nm and the length in the circumferential direction of the concave portion was 150 nm (concavo-convex ratio of 0.60) (working example 1-1) and when the length in the circumferential direction of the convex portion of the burst pattern was 300 nm and the length in the circumferential direction of the concave portion was 100 nm (concavo-convex ratio of 0.33) (working example 1-2). In contrast, in a conventional magnetic recording and reproducing apparatus, position error signals were measured when the length in the circumferential direction of the convex portion of each of the burst patterns were 200 nm and the length in the circumferential direction of the concave portion was 200 nm (concavo-convex ratio of 1.00).

More specifically, as shown inFIG. 8, four burst signal groups110A,110B,110C, and110D were formed as position information on the magnetic recording medium (one burst signal group was shown with one block inFIG. 8for convenience). A position error signal Sab obtained from the burst signal groups110A and110B and a position error signal Scd obtained from the burst signal groups110C and110D both obtained during the movement of the magnetic head were measured. Here, the position error signal Sab is obtained as (Sa−Sb)/(Sa+Sb), where the output of the position control signal of the burst signal group110A and that of the burst signal group110B are assumed to be Sa and Sb, respectively. Similarly, the position error signal Scd is obtained as (Sc−Sd)/(Sc+Sd), where the output of the position control signal of the burst signal group110C and that of the burst signal group110D are assumed to be Sc and Sd, respectively.

The graph inFIG. 8shows a relationship between the magnetic head position and the position error signal Sab and Scd in the working example 1-1 and the conventional example as a comparative example. And the graph inFIG. 9shows a relationship between the magnetic head position and the position error signal Sab and Scd in the working example 1-2 and the conventional example as a comparative example. A line sloping upwards (magnetic head position: 10 nm to 110 nm) inFIG. 9represents the position error signal Sab and a line sloping downwards (magnetic head position: 110 nm to 210 nm) represents the position error signal Scd. As shown inFIG. 10, the position of the magnetic head in the graph shows an interval between the left end of the burst signal group110A and the right end of the magnetic head.

As shown inFIG. 8andFIG. 9, it was confirmed that the position error signal of the magnetic recording and reproducing apparatus of the first exemplary embodiment had linearity that was substantially the same as that of the position error signal of the conventional magnetic recording and reproducing apparatus.

As described above, according to the magnetic recording and reproducing apparatus and the control method for the same of the first exemplary embodiment, it is possible to make the output of the position control signal larger and perform positioning control with high precision, while keeping the linearity of the position error signal.

FIG. 11is a block diagram of a position control circuit40in the magnetic recording and reproducing apparatus (not shown in the figure) according to a second exemplary embodiment of the present invention.

In place of the signal processing circuit12of the first exemplary embodiment, the magnetic recording and reproducing apparatus according to the second exemplary embodiment is equipped with a signal processing circuit42. The remaining configuration is identical to the first exemplary embodiment.

This signal processing circuit42comprises a signal extractor (signal extraction device)44that extracts signal which contain fundamental wave component and second order harmonic component from reproduced signal of position information, and an amplitude detector (amplitude detection device)46that detects the amplitude values of the signal and generates position control signal.

The signal extractor44is composed of a LPF44A that removes frequency components at regions higher than the second order harmonic component of the reproduced signal and a HPF44B that removes frequency components at regions lower than the fundamental wave component of the reproduced signal.

The amplitude detector46detects amplitude values of signal which contain fundamental wave component and second order harmonic component extracted by the signal extractor44and then generates position control signal.

In the magnetic recording and reproducing apparatus according to the second exemplary embodiment, the signal processing device (the signal processing circuit42in the second exemplary embodiment) is composed of signal extraction device (the signal extractor44in the second exemplary embodiment) that extracts signal which contain fundamental wave component and at least one harmonic component from reproduced signal of position information, and amplitude detection device (the amplitude detector46in the second exemplary embodiment) that detects amplitude values of the signal and generates position control signal. Thus, the circuitry can be simplified compared to the magnetic recording and reproducing apparatus according to the first exemplary embodiment. The magnetic recording and reproducing apparatus according to the second exemplary embodiment is suitable when there is only a little noise of reproduced signal of position information.

FIG. 12is a block diagram of a position control circuit50in the magnetic recording and reproducing apparatus (not shown in the figure) according to a third exemplary embodiment of the present invention.

In place of the signal processing circuit12of the first exemplary embodiment, the magnetic recording and reproducing apparatus according to the third exemplary embodiment is equipped with a signal processing circuit52. The remaining configuration is identical to the first exemplary embodiment.

This signal processing circuit52is composed of a frequency analyzer (frequency analyzing device)54that analyzes the frequency of the reproduced signal of the position information and then detects the respective amplitude values of the fundamental wave component and second order harmonic component in this reproduced signal, and an adder (signal adding device)56that adds the respective amplitude values and generates position control signal.

The frequency analyzer54analyzes the frequency of the reproduced signal of the position information and then detects the respective amplitude values of the fundamental wave component and second order harmonic component in the reproduced signal.

The signal adder56adds the amplitude values of the fundamental wave component and the amplitude values of the second order harmonic component detected by the frequency analyzer54and then generates position control signal.

In the magnetic recording and reproducing apparatus according to the third exemplary embodiment, the signal processing device (the signal processing circuit52in the third exemplary embodiment) is composed of frequency analyzing device (the frequency analyzer54in the third exemplary embodiment) that analyzes the frequency of the reproduced signal of the position information and then detects respective amplitude values of the fundamental wave component and at least one harmonic component in this reproduced signal, and signal adding device (the signal adder56in the third exemplary embodiment) that adds the respective amplitude values and generates position control signal. Thus, noise included in the frequency components other than the fundamental wave component and the harmonic component of the reproduced signal can be reliably eliminated and stabilized position control signal can be achieved.

The magnetic recording and reproducing apparatus and the control method thereof according to the present invention are not limited to those shown in the first to third exemplary embodiments.

Consequently, although position control signal is generated based on amplitude values of fundamental wave component and second order harmonic component in the reproduced signal of position information by the above-mentioned signal processing circuits12,42, or52, for example, position control signal can also be generated based on amplitude values of Nth order harmonic components (N being an integer equal to 3 or more) in addition to amplitude values of fundamental wave component and second order harmonic component or position control signal can be generated based on amplitude values of fundamental wave component and Nth order harmonic component excluding second order harmonic component. In other words, the signal processing device according to the present invention can generate position control signal based on amplitude values of fundamental wave component and at least one harmonic component in the reproduced signal of position information.

The magnetic recording medium is not limited to a perpendicular recording medium. The present invention can be also applied to a longitudinal recording medium. For this case, it is preferable to arrange an integrator between the amplifier116and the signal processing circuit12(42,52) in the first to third exemplary embodiments to integrate the reproduced signal waveforms of the position information in the longitudinal recording medium, thereby providing a waveform shape identical to the reproduced signal waveform of the position information in the perpendicular magnetic recording medium.

The “concavo-convex pattern” in the present invention is not limited to that described in the first exemplary embodiment. For example, as shown inFIG. 13, a concavo-convex pattern40may be formed by forming a magnetic layer44to cover a concavo-convex pattern formed on a substrate42. In the concavo-convex pattern40, the magnetic layer44forms not only convex portions40A but also bottom of concave portions40B. Alternatively, as shown inFIG. 14, a magnetic layer52may form a concavo-convex pattern50including not only convex portions50A but also bottoms of concave portions50B. Moreover, the convex portions shown inFIG. 3(mesh portions inFIG. 3) may be changed into concave portions of the concavo-convex pattern (white portions inFIG. 15). For this case, since the portion that is the concave portion inFIG. 3is composed of a convex portion formed of a magnetic layer, the base of the output values for the reproduced signal of the concavo-convex pattern entirely rises upward as shown inFIG. 16. However, it is thought that if the concavo-convex ratio BL2/BL1in an identical burst signal group is the same, the waveform of the reproduced signal itself will not be different from one generated by the concavo-convex pattern ofFIG. 3thereby making it possible to obtain results identical to the first to third exemplary embodiments with the concavo-convex ratio BL2/BL1in an identical burst signal group being within a range of larger than 0.19 and smaller than 1.

In the first to third exemplary embodiment, application example to a discrete track medium having a user data region in which concentric recording tracks are formed by convex portions formed by a magnetic layer and are magnetically separated from each other by a plurality of concentric grooves (i.e., concave portions of a concavo-convex pattern) are shown. However, the present invention is not limited thereto.

For example, the present invention can be applied to a so-called patterned medium in which convex portions formed by sectioning a magnetic layer in a mesh-like pattern or a dot pattern (i.e., dividing each recording track into a plurality of parts in the circumferential direction in such a manner that those parts are magnetically separated from each other) are isolated from each other like islands. Moreover, the magnetic layer in the user data region may be formed by a continuous magnetic layer in which no concavo-convex pattern is formed.

In the first exemplary embodiment, the burst pattern formed by four burst signal groups110A,110B,110C, and110D is formed as position information on the magnetic recording medium. However, the present invention is not limited thereto. For example, a burst pattern may be formed to include a pair of burst signal groups110A and110B only. In addition, the arrangement of the burst signal groups with respect to the data tracks is not limited specifically. For example, a pair of position information, i.e., the burst signal groups110A and110B may be arranged at positions shifted from positions of another pair of position information, i.e., the burst signal groups110C and110D by one third of the track pitch.

The present invention can be applied to a magnetic recording and reproducing apparatus equipped with a magnetic recording medium such as a discrete track medium or patterned medium and a control method thereof, a magnetic recording medium, and a stamper for manufacturing of the magnetic recording medium.