JP5188770B2 - Magnetic disk evaluation method - Google Patents

Description

  The present invention relates to a magnetic disk evaluation method for evaluating a track profile of a magnetic disk formed in a disk shape.

  In recent years, with the advancement of information technology, information recording technology, particularly magnetic recording technology, has made remarkable progress. As a substrate for a magnetic disk such as a hard disk drive (HDD) which is one of such magnetic recording media, an aluminum substrate has been widely used. However, with the downsizing, thinning, and high recording density of magnetic disks, there is an increasing demand for glass substrates that have superior substrate surface flatness and substrate strength compared to aluminum substrates.

  Particularly in recent years, in order to further improve the recording density, a perpendicular magnetic recording method in which the recording layer is magnetized in the direction perpendicular to the magnetic disk plane is being adopted. Under these circumstances, in order to further increase the recording density of the magnetic disk, both the linear recording density in the circumferential direction (BPI: Bit Per Inch) and the track recording density in the radial direction (TPI: Track Per Inch) We must improve.

  Incidentally, magnetic recording / reproducing heads for recording / reproducing signals on such magnetic disks have come to perform recording and reproduction with separate heads as the magnetic recording technology becomes more dense. Therefore, in recent years, as shown in FIG. 10, a recording head 20 such as a single pole head or a trailing shield head, and a reproducing head 22 such as a large magnetoresistive (GMR) head or a tunnel magnetoresistive (TuMR) head. And are arranged separately.

  The recording head 20 and the reproducing head 22 separated in this way are arranged on a straight line in the slider, but the track for recording and reproducing is formed circumferentially along the magnetic disk. In order to arrange the recording head 20 and the reproducing head 22, the reproducing head 22 needs to be offset from the recording head 20 on the radially inner side by, for example, about 160 nm at the maximum.

  Referring to FIG. 11, in the slider 24, the recording head 20 and the reproducing head 22 mounted on the straight line extending in the longitudinal direction of the suspension 26 are in a state in which no offset movement is performed, and another track on the magnetic disk 28. 30 and 32. Accordingly, in order to reproduce the signal recorded on the track 30 by the recording head 20, the reproducing head 22 must move from the track 32 to the track 30 with a predetermined amount of offset 40.

  The value of the offset of the reproducing head 22 is obtained through actual signal recording / reproduction. For example, the magnetic disk is rotated to record a signal from the recording head 20 to a predetermined on-track position, and then the reproducing head is moved to search for a position where the reproduction output of the recorded signal is maximized. The amount of movement of the reproducing head 22 for this search becomes the offset value as it is. This offset is stored in the magnetic disk device, and the recorded signal is accurately reproduced by moving the reproducing head in advance by the stored offset during the next reproduction.

  However, there may be a difference between the set offset and the actual offset due to a search error at the position where the output signal becomes maximum, a temperature change of the magnetic disk device, an offset drift with time, and the like. In the conventional magnetic disk having a low recording density, the track interval is wide and the recordable width in the radial direction is wide, and thus some errors in such an offset are allowed.

  However, in recent years, the influence of such an offset error cannot be ignored in a high recording density magnetic disk. For example, on a magnetic disk having a short recordable width, recording may occur at a position other than the recording area (recordable width) due to an offset error, and the signal may be buried in noise and the reproducing head may not be able to identify the signal. Accordingly, it has become necessary to ensure the maximum recordable width in the radial direction while increasing the track recording density.

  In order to estimate the recordable width of such a magnetic disk, an off-track signal different from on-track is intentionally recorded on both sides of the on-track, and the on-track signal can be identified from the off-track signal. Is known, and this limit position is derived as an off-track margin (Patent Document 1).

  However, the technique for deriving such an off-track margin merely derives a boundary line with an off-track signal intentionally recorded in an area adjacent to the track, and noise (leakage from the adjacent track). The influence of the magnetic field cannot be measured.

Here, the necessity of securing a certain recordable width has been described. However, when the track recording density TPI is increased, the attempt to simply ensure the recordable width increases the overall track width. , The influence on the adjacent track will become large. If this influence is great, the stored contents of the adjacent track will be erased, or the reproduction output will become unstable. Therefore, a magnetic disk that has a small effect on adjacent tracks while ensuring a recordable width is desired.
JP-A-6-84149

  In recent magnetic disks adopting the perpendicular magnetic recording system, a storage capacity exceeding 160 GB is required for one 2.5-inch diameter magnetic disk, and the track width is reduced accordingly, so that the reproduction output of the own track can be achieved. This greatly affects the noise of adjacent tracks. Therefore, in order to obtain a magnetic disk that can cope with higher recording density, it is necessary to select a magnetic disk that has less influence on adjacent tracks from the generated magnetic disk. In order to identify such a high-quality magnetic disk at an early stage of the manufacturing process, it is necessary to evaluate the spread of the track profile in which the reproduction output is plotted in the track direction, that is, the track width of the region where the reproduction output is small. come.

  As an evaluation of the track width, an approximate straight line of a curve of 20 to 80% of the track profile is derived, and the track width MWW (Magnetic Write Width) corresponding to 50% of the track profile is the midpoint of the approximate straight line. There is a way to define the length. However, this method is a method for evaluating the memorable width, and does not measure a quantitative spread of the base when the track profile is regarded as a mountain. For example, in the magnetic disks having the same MWW, the spread of the skirt may be different, and the influence on the adjacent track may not be evaluated only by the MWW.

  As other evaluation methods, there are Squash, Erase Band, ATI, WATE, and the like for sequentially writing signals to the on-track position and ± 90% of the center of the track and measuring the signal attenuation rate at the on-track position. However, in these evaluation methods, it takes a long time to evaluate, for example, it is necessary to write three tracks in one test.

  As a result of earnestly examining the above problem, the present inventor has evaluated the track width at a position where the reproduction output has been ignored until now, that is, the substantial spread of the track profile, thereby increasing the recording density. The inventors have found that it is possible to quickly select a tolerable magnetic disk, and have succeeded in easily grasping the recording characteristics of the adjacent tracks of the magnetic disk, which could not be measured in the past, thereby completing the present invention.

  The present invention has been made in view of the above-described problems of conventional evaluation methods, and an object of the present invention is to quickly and reliably extract a magnetic disk that can cope with higher recording density in a short time. It is an object of the present invention to provide a new and improved method for evaluating a magnetic disk that can be performed.

  In order to solve the above-described problems, according to one aspect of the present invention, there is provided a magnetic disk evaluation method for evaluating a track profile of a magnetic disk formed in a disk shape. A signal recording process in which a test signal having a specific frequency is recorded on the magnetic disk at an arbitrary position by moving in the radial direction of the magnetic disk, and a reproduction output of the recorded signal while moving the reproducing head in the radial direction of the magnetic disk. A signal measurement step for continuously measuring and generating a track profile, a track width deriving step for deriving a track width at any arbitrary percentage within a range of 0 to 20% of the maximum value of the track profile, and And a track width determining step for determining whether or not the track width is within a predetermined value. Evaluation method is provided.

  With the configuration in which the track width in any arbitrary% within the range of 0 to 20% is derived, it is possible to quantitatively evaluate the spread of the bottom of the track profile that has been ignored until now. Here, it is determined that the smaller the track width, the less influence on the adjacent track.

  Further, since the recording characteristics can be evaluated by writing to a single track without writing signals to a plurality of tracks, the evaluation time can be remarkably shortened. Furthermore, if a track profile has already been generated for other evaluation purposes, for example, a storable width test, the track profile can be applied to the present invention as it is, so that the evaluation time can be further shortened. It becomes.

  The track width may be the length between the midpoints of a predetermined range of two approximate straight lines of the track profile in a predetermined range within 0 to 20%.

  By canceling the fluctuation of the track profile using such an approximate straight line and making the track profile uniform within a predetermined range, it is possible to identify an appropriate position of arbitrary% as the midpoint, and derive an accurate track width. It becomes possible.

  The predetermined range is 0 to 2%, and the arbitrary% may be 1%. In the above-described invention, the track width is derived within a predetermined range of 0 to 20%. However, the smaller the arbitrary% is, the more accurately the width of the base can be grasped, and the evaluation accuracy becomes higher. Therefore, by deriving the track width at the midpoint (1%) of the approximate straight line with a predetermined range of 0 to 2%, the performance of the magnetic disk can be more accurately evaluated.

  The predetermined value may be twice the track width at 50% of the maximum value of the track profile. By providing the relative evaluation criteria for the track width in this way, a uniform evaluation can be executed regardless of the track recording density TPI.

  In order to solve the above problems, according to another aspect of the present invention, there is provided a magnetic disk evaluation method for evaluating a track profile of a magnetic disk formed in a disk shape, wherein the magnetic disk is rotated and the recording head is rotated. Is recorded in the radial direction of the magnetic disk, and a signal recording process for recording a test signal of a specific frequency on the magnetic disk at an arbitrary position, and reproduction output of the recorded signal while moving the reproducing head in the radial direction of the magnetic disk A signal measurement step for continuously measuring the track profile to generate a track profile, and a derivative value deriving step for deriving a derivative value at any arbitrary percentage within a range of 0 to 20% of the maximum value of the track profile. And a differential value determining step of determining whether or not the differential value is equal to or greater than a predetermined value.

  When accurate evaluation is difficult by the above-described magnetic disk evaluation method for deriving the track width at an arbitrary%, or when it is difficult to generate an approximate line, a differential value at an arbitrary% can be used as a supplementary means. . With such a differential value, it is possible to estimate the extent of the base from the tangent line of the track profile at an arbitrary%, and it can be determined that the higher the differential value, the less influence on the adjacent track.

  As described above, according to the present invention, it is possible to quickly and reliably extract a magnetic disk that can cope with an increase in recording density in a short time. The extracted magnetic disk can also be applied to uses that require high recording density and low error rate.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  As described above, magnetic disks for magnetic recording media such as HDDs are becoming smaller and thinner, and recently, in order to further improve the recording density, the recording film is perpendicular to the film plane. A perpendicular magnetic recording method for magnetizing the magnetic disk is also adopted. Of course, a perpendicular magnetic recording type magnetic disk formed so as to cope with higher recording density needs to be evaluated by an excellent evaluation method applicable to such a higher recording density magnetic disk. . Here, in order to facilitate understanding of the present embodiment, the composition of the magnetic disk by the perpendicular magnetic recording method will be briefly described, and thereafter, an excellent evaluation method in the embodiment of the present invention will be described.

(Magnetic disk)
FIG. 1 is a cross-sectional view showing the structure of a magnetic disk 50 according to the perpendicular magnetic recording system. Such a perpendicular magnetic recording type magnetic disk 50 includes a disk substrate 52, an adhesion layer 54, a soft magnetic layer 56, an orientation control layer 58, an underlayer 60, a magnetic recording layer 62, a continuous layer 64, a medium protective layer 66, and a lubricating layer 68. It consists of

  First, an amorphous aluminosilicate glass is formed into a disk shape by direct pressing to produce a glass disk. The glass disk is subjected to grinding, polishing, and chemical strengthening sequentially to obtain a smooth non-magnetic disk base 52 made of a chemically strengthened glass disk. On the obtained disk substrate 52, a film forming apparatus that is evacuated is used to sequentially form a film from the adhesion layer 54 to the continuous layer 64 by a DC magnetron sputtering method in an Ar atmosphere. A film is formed by a CVD method. Thereafter, the lubricating layer 68 is formed by dip coating. Hereinafter, the configuration of each layer will be described.

  The adhesion layer 54 was formed using a Ti alloy target so as to be a 10 nm Ti alloy layer. Adhesion between the disk substrate 52 and the soft magnetic layer 56 is improved. The soft magnetic layer 56 is configured to include AFC (Antiferro-magnetic exchange coupling) in two layers with a spacer layer (not shown) interposed therebetween. As a result, the magnetization direction of the soft magnetic layer 56 can be aligned with high accuracy along the magnetic path (magnetic circuit), and the vertical component of the magnetization direction is extremely reduced, so that noise generated from the soft magnetic layer 56 is reduced. Can do. The orientation control layer 58 has a function of protecting the soft magnetic layer 56 and a function of promoting alignment of crystal grain orientation of the underlayer 60. The underlayer 60 has an hcp structure, and the crystal of the hcp structure of the magnetic recording layer 62 can be grown as a granular structure.

The magnetic recording layer 62 is formed of a magnetic recording layer having a granular structure in which magnetic particles are magnetically isolated. Specifically, an hcp crystal structure is formed using a hard magnetic target made of CoCrPt containing SiO ₂ as an example of a nonmagnetic substance. The continuous layer 64 forms a thin film (auxiliary recording layer) exhibiting high perpendicular magnetic anisotropy on the granular magnetic layer to constitute a CGC structure (Coupled Granular Continuous).

  The medium protective layer 66 is formed by depositing carbon by CVD and contains diamond-like carbon, and protects the magnetic disk 50 from the impact of the magnetic head. The lubricating layer 68 is a layer in which PFPE (perfluoropolyether) is formed by dip coating.

  Such a perpendicular magnetic recording type magnetic disk 50 can obtain high TPI and BPI because the demagnetizing field decreases as the recording density increases. The present embodiment aims to achieve a high recording density of, for example, 150 kTPI or more with the perpendicular magnetic recording type magnetic disk 50 thus formed. At this time, a problem is noise (recording blur) that occurs in adjacent tracks due to writing to the tracks of the magnetic disk 50.

  FIG. 2 is an explanatory diagram showing the locus of the recording / reproducing head on the magnetic disk 50, and FIG. 3 is an explanatory diagram schematically showing the reproduction output of the signal in the radial direction of the magnetic disk. As shown in FIG. 2, each recording head continuously records information of 1 bit 80 along the track of the magnetic disk 50, and the reproducing head preferably moves to the radial center 82 of the recorded signal. To play back the signal.

  The reproduced signal is measured by a spin stand (electromagnetic conversion characteristic evaluation apparatus) while shifting the magnetic head in the radial direction (track direction), and forms a track profile 90 as shown by a thick line in FIG. The track profile 90 is a locus of the reproduction output value in the track width direction. By using the track profile 90, the reproduction output distribution in the track direction can be grasped.

  As shown in FIG. 3, for example, when a recording signal 94 recorded by a recording head having a width 92 of 180 nm is reproduced by a reproducing head, the track profile 90 gradually decreases as the distance from the center 96 of the recording signal 94 increases in the radial direction. Attenuate along. This attenuation indicates that the force for holding the recording signal is weak at a position away from the center 96. Here, the 50% output point between the maximum values of the track profile 90 is referred to as MWW (Magnetic Write Width). The MWW is precisely the length between the midpoints (50%) of the approximate straight lines of the left and right curves of 20 to 80% in the track profile, and is almost equal to the width of the recording signal 94.

  Thus, the track profile 90 in the recording signal 94 becomes weaker in magnetism as the distance from the recording signal center 96 increases. On the other hand, the track profile 90 outside the recording signal 94 exists widely even at a position beyond the recording signal 94, and this wide reproduction signal becomes noise of adjacent tracks. In recent magnetic disks in which the distance between tracks is close, such noise affects the reproduction signal of the adjacent track, reducing the recordable width.

  Therefore, while the track recording density is improved, it is necessary to prevent the signal written on the own track from affecting the adjacent track. However, in the conventional evaluation method, the base portion of the track profile 90 (reproduction output is small). There was no method for quantitatively evaluating (part). The inventor of the present application quickly selects a magnetic disk that can withstand higher recording density by evaluating the track width at a position where the reproduction output has been ignored, that is, the substantial base of the track profile, which has been ignored until now. I found out that I can do it.

(Evaluation method of magnetic disk: Evaluation by track width)
FIG. 4 is a flowchart showing the flow of the magnetic disk evaluation method according to the present embodiment. In the magnetic disk evaluation method for evaluating the track profile of the magnetic disk, first, initialization by AC erase is performed (S100), the magnetic disk 50 assembled as a magnetic disk device is rotated, and the recording head is moved to the magnetic disk 50. After moving in the radial direction and stopping at an arbitrary position on the magnetic disk, a test signal having a specific frequency, here, a low frequency is recorded on the magnetic disk 50 (S102). In low-frequency writing, the frequency of change of data to be written is reduced and the track profile 90 is likely to spread. Therefore, the evaluation of the present embodiment is performed under such bad conditions.

  Next, the reproduction output of the signal recorded by the recording head is continuously measured while moving the reproduction head in the radial direction of the magnetic disk 50, and the track profile 90 is generated (S104).

  FIG. 5 is an explanatory diagram schematically showing a track profile (reproduction output) of the magnetic disk 50. Here, a track profile 90 for a recording signal 150 recorded by the recording head is shown. The maximum output point of the track profile 90 is the on-track position 152, which is a reference for the reproduction output ratio (%).

  Subsequently, the track width Tw (Fringing Trach Width) at any arbitrary% within the range 154 that becomes 0 to 20% of the maximum value of the track profile 90, for example, 1% is derived (S106). The track width Tw is a straight line connecting midpoints (1%) of the predetermined range 0 to 2% of the two approximate straight lines 160 of the track profile 90 in a predetermined range within 0 to 20%, for example, 0 to 2% in FIG. Length.

The degree of approximation of the approximate line 160 is evaluated by the square of the correlation coefficient R between the track profile 90 and the approximate line 160 (perfect match when R ² = 1). However, since the target track profile 90 draws a smooth curve, the degree of approximation decreases if an approximate straight line is obtained over a wide range. In order to evaluate the present embodiment, provided that R ² is 0.9 or more. In the case of FIG. 5, R ² is 0.98, which satisfies this condition.

  By canceling the fluctuation of the track profile 90 using such an approximate straight line 160 and making the track profile 90 uniform within a predetermined range, it is possible to specify an appropriate position of an arbitrary% as the midpoint, and an accurate track width Tw can be derived.

  With the configuration for deriving the track width Tw at any arbitrary percentage within the range of 0 to 20%, it is possible to quantitatively evaluate the spread of the bottom of the track profile 90 that has been ignored so far. Here, it is determined that the smaller the track width Tw, the less the influence on the adjacent track.

  Further, since the recording characteristics can be evaluated by writing to a single track without writing signals to a plurality of tracks, the evaluation time can be remarkably shortened. In addition, when the track profile 90 is generated in parallel for other evaluation purposes, for example, a storable width test, the track profile 90 can be directly applied to the present embodiment, so that the evaluation time can be further shortened. It becomes.

  Here, the reason why the arbitrary% is 1% is that the smaller the arbitrary% is, the more accurately the width of the base can be grasped, and the evaluation accuracy becomes higher. Further, since the track profile 90 has an inflection point around 5% and transitions in a substantially straight line at 0 to 2%, the accuracy of the approximate straight line becomes high. Therefore, by deriving the track width at the midpoint (1%) of the approximate straight line with a predetermined range of 0 to 2%, the performance of the magnetic disk can be more accurately evaluated.

  Finally, it is determined whether or not the track width Tw derived in the track width deriving step (S106) is within a predetermined value (S108). In the track width determination step (S108), it is confirmed whether the track width Tw is within a predetermined value, that is, whether the signal written in the own track does not affect the adjacent track.

  The predetermined value in this embodiment is set to twice the track width MWW (Tw ≦ 2 × MWW) at 50% of the maximum value of the track profile 90.

  FIG. 6 is an explanatory diagram for explaining an evaluation condition for a track width Tw of 0 to 20%. If the track width Tw of 0 to 20%, especially 1% is less than or equal to twice the track width MWW of 50%, there is little influence on the adjacent track 170 and the two adjacent tracks 172 are not superimposed. However, since the reproduction output of 1% or less may be further spread, the track profile 90 of its own and the two adjacent track profiles 90 may be overlapped.

  By providing a relative evaluation standard for the track width Tw in this way, a uniform evaluation can be executed regardless of the track recording density TPI.

(Evaluation by differential value)
When accurate evaluation is difficult by the above-described magnetic disk evaluation method for deriving the track width at an arbitrary%, or when it is difficult to generate an approximate line, a differential value at an arbitrary% can be used as a supplementary means. .

  FIG. 7 is a flowchart showing the flow of another evaluation method of the magnetic disk according to the present embodiment. A part of the magnetic disk evaluation method for evaluating the track profile 90 of the magnetic disk is substantially the same as steps S100 to S108 already described with reference to FIG. Mainly explained.

  In the track width determination step S108, if the result does not reach an accurate determination, the track profile 90 is used to derive a differential value in any arbitrary% within the range of 0 to 20% of the maximum value ( S110). When evaluating a differential value here, the absolute value is taken and evaluated.

  FIG. 8 is an explanatory diagram showing the differential value of the track profile 90. In FIG. 8, the trajectory of the track profile 90 is shown upward, and the differential value is shown downward. Here, since the left and right waveforms of the on-track position 152 of the track profile 90 are slightly different, the differential value 180 on the left of the track profile 90 and the differential value 182 on the right are also different. Accordingly, the differential value S1 and the differential value Sr of, for example, 1% within the range of 0 to 20% also show different values although they are substantially the same level.

  Then, it is determined whether or not the differential values S1 and Sr derived in the differential value deriving step S110 are greater than or equal to a predetermined value (S112). With such a differential value, it is possible to estimate the extent of the base from the tangent (inclination) of the track profile 90 at an arbitrary%, and it can be determined that the higher the differential value, the less the influence on adjacent tracks. By adding the evaluation based on such a differential value to the above-described evaluation of the track width Tw, it is possible to reliably grasp the extent of the base of the track profile 90.

  Further, as described above, the track width Tw and the differential values S1 and Sr may be evaluated by an absolute value or a relative value, or may be evaluated by superiority or inferiority relative to other magnetic disks. In the above-described embodiment, the evaluation of the differential values S1 and Sr is performed after the evaluation of the track width Tw. However, the processing order may be reversed, and the evaluation of the differential values S1 and Sr is performed. It may be done alone.

(Example)
Hereinafter, two magnetic disks having the same 50% track width MWW were evaluated using the evaluation method of this embodiment. First, both magnetic disks were AC erased and a low frequency signal was written by the recording head. The written signal was read while shifting in the radial direction to generate two track profiles.

  FIG. 9 is an explanatory diagram showing track profiles 90A and 90B of the two magnetic disks. As shown in FIG. 9A, the two track profiles 90A and 90B relating to the two magnetic disks have the same width of 50% track width MWW but different base spreads. When the 1% track width Tw and the differential values Sl and Sr were measured based on the evaluation method of the present embodiment, the result as shown in FIG. 9B was obtained. Here, the track profile 90A has a narrower track width Tw than the track profile 90B (see TwA and TwB), and the differential values S1 and Sr are larger (see S1A, S1B and SrA and SrB). Therefore, it can be understood that the influence of adjacent tracks is small.

  As described above, according to the magnetic disk evaluation method of the present embodiment, the track profile that has been ignored so far is derived by deriving the track width in any arbitrary% within the range of 0 to 20%. It is possible to quantitatively evaluate the spread of the base of the. Further, since the recording characteristics can be evaluated by writing to a single track without writing signals to a plurality of tracks, the evaluation time can be remarkably shortened. Furthermore, the track profile of the magnetic disk can be more reliably evaluated by supplementing the evaluation based on the track width with the evaluation based on the differential value.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  Note that the steps in the magnetic disk evaluation method of the present specification do not necessarily have to be processed in chronological order according to the order described in the flowchart, and are executed in parallel or individually (for example, parallel processing or Object processing) may also be included.

  The present invention is applicable to a magnetic disk evaluation method for evaluating a track profile of a magnetic disk formed in a disk shape.

It is sectional drawing which showed the structure of the magnetic disc by a perpendicular magnetic recording system. It is explanatory drawing which showed the locus | trajectory on the magnetic disc of a recording / reproducing head. It is explanatory drawing which showed typically the reproduction output of the signal of a magnetic disc radial direction. It is the flowchart which showed the flow of the evaluation method of a magnetic disc. It is explanatory drawing which showed typically the track profile of a magnetic disc. It is explanatory drawing for demonstrating the evaluation conditions of 0-20% track width Tw. 6 is a flowchart showing the flow of another evaluation method of the magnetic disk according to the present embodiment. It is explanatory drawing which showed the differential value of the track profile. It is explanatory drawing which showed the track profile of two such magnetic discs. It is the perspective view which showed the separated magnetic recording / reproducing head. It is explanatory drawing which showed the positional relationship of a recording head and a reproducing head.

Explanation of symbols

Sl, Sr ... Differential value TW ... Track width 160 ... Approximate line 90 ... Track profile

Claims (5)

A magnetic disk evaluation method for evaluating a track profile of a magnetic disk formed in a disk shape,
A signal recording step of rotating the magnetic disk, moving the recording head in the radial direction of the magnetic disk, and recording a test signal of a specific frequency on the magnetic disk at an arbitrary position;
A signal measuring step of continuously measuring the reproduction output of the recorded signal and generating a track profile while moving the reproducing head in the radial direction of the magnetic disk;
A track width deriving step of determining an arbitrary reproduction output as a track width in a range of 0 to 20% of the maximum value of the reproduction output of the track profile;
A track width determining step of determining whether or not the derived track width is within a predetermined value;
A method for evaluating a magnetic disk, comprising:

  2. The magnetic disk according to claim 1, wherein the track width is a length between midpoints of the two predetermined approximate ranges of the track profile in the predetermined range within the range of 0 to 20%. Evaluation method. 3. The magnetic disk evaluation method according to claim 2, wherein the predetermined range is 0 to 2%, and the reproduction output is 1% of a maximum value .   4. The magnetic disk evaluation method according to claim 1, wherein the predetermined value is twice the track width at 50% of the maximum value of the track profile. A magnetic disk evaluation method for evaluating a track profile of a magnetic disk formed in a disk shape,
A signal recording step of rotating the magnetic disk, moving the recording head in the radial direction of the magnetic disk, and recording a test signal of a specific frequency on the magnetic disk at an arbitrary position;
A signal measuring step of continuously measuring the reproduction output of the recorded signal and generating a track profile while moving the reproducing head in the radial direction of the magnetic disk;
A differential value derivation step of deriving a differential value by determining an arbitrary reproduction output in a range of 0 to 20% of the maximum value of the reproduction output of the track profile;
A differential value determining step of determining whether the derived differential value is greater than or equal to a predetermined value;
A method for evaluating a magnetic disk, comprising:

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