US20040010391A1 - Method and apparatus for determining the magnetic track width of a magnetic head - Google Patents
Method and apparatus for determining the magnetic track width of a magnetic head Download PDFInfo
- Publication number
- US20040010391A1 US20040010391A1 US10/193,514 US19351402A US2004010391A1 US 20040010391 A1 US20040010391 A1 US 20040010391A1 US 19351402 A US19351402 A US 19351402A US 2004010391 A1 US2004010391 A1 US 2004010391A1
- Authority
- US
- United States
- Prior art keywords
- magnetic head
- magnetic
- determining
- ftp
- head positions
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000012937 correction Methods 0.000 claims abstract description 39
- 238000004590 computer program Methods 0.000 claims 7
- 238000012360 testing method Methods 0.000 abstract description 2
- 238000004458 analytical method Methods 0.000 description 7
- 238000007796 conventional method Methods 0.000 description 6
- 239000010432 diamond Substances 0.000 description 6
- 238000004364 calculation method Methods 0.000 description 5
- 101000606504 Drosophila melanogaster Tyrosine-protein kinase-like otk Proteins 0.000 description 4
- 230000008859 change Effects 0.000 description 4
- 238000009413 insulation Methods 0.000 description 3
- 230000005415 magnetization Effects 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- 235000012431 wafers Nutrition 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000002772 conduction electron Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000005316 response function Methods 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/10009—Improvement or modification of read or write signals
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/012—Recording on, or reproducing or erasing from, magnetic disks
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/455—Arrangements for functional testing of heads; Measuring arrangements for heads
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B2005/0002—Special dispositions or recording techniques
- G11B2005/0005—Arrangements, methods or circuits
- G11B2005/001—Controlling recording characteristics of record carriers or transducing characteristics of transducers by means not being part of their structure
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B2005/0002—Special dispositions or recording techniques
- G11B2005/0005—Arrangements, methods or circuits
- G11B2005/001—Controlling recording characteristics of record carriers or transducing characteristics of transducers by means not being part of their structure
- G11B2005/0013—Controlling recording characteristics of record carriers or transducing characteristics of transducers by means not being part of their structure of transducers, e.g. linearisation, equalisation
- G11B2005/0016—Controlling recording characteristics of record carriers or transducing characteristics of transducers by means not being part of their structure of transducers, e.g. linearisation, equalisation of magnetoresistive transducers
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/488—Disposition of heads
- G11B5/4886—Disposition of heads relative to rotating disc
Landscapes
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Digital Magnetic Recording (AREA)
Abstract
Description
- 1. Field of the Invention
- This invention relates to methods and apparatus for determining the magnetic track width of a magnetic head.
- 2. Description of the Related Art
- A write head is typically combined with a magnetoresistive (MR) or giant magnetoresistive (GMR) read head to form a merged head, certain elements of which are exposed at an air bearing surface (ABS). The write head is made of first and second pole pieces having first and second pole tips, respectively, which terminate at the ABS. The first and second pole pieces are connected at the yoke by a back gap, whereas the first and second pole tips are separated by a non-magnetic gap layer. An insulation stack, which comprises a plurality of insulation layers, is sandwiched between the first and second pole pieces, and a coil layer is embedded in this insulation stack. A processing circuit is connected to the coil layer for conducting write current through the coil layer which, in turn, induces write fields in the first and second pole pieces. Thus, write fields of the first and second pole tips at the ABS fringe across the gap layer. In a magnetic disk drive, a magnetic disk is rotated adjacent to, and a short distance (fly height) from, the ABS so that the write fields magnetize the disk along circular tracks. The written circular tracks then contain information in the form of magnetized segments with fields detectable by the read head.
- An MR read head includes an MR sensor sandwiched between first and second non-magnetic gap layers, and located at the ABS. The MR sensor detects magnetic fields from the circular tracks of the rotating disk by a change in resistance that corresponds to the strength of the fields. A sense current is conducted through the MR sensor, where changes in resistance cause voltage changes that are received by the processing circuitry as readback signals. On the other hand, a GMR read head includes a GMR sensor which manifests the GMR effect In the GMR sensor, the resistance of the MR sensing layer varies as a function of the spin-dependent transmission of the conduction electrons between magnetic layers separated by a non-magnetic layer (spacer) and the accompanying spin-dependent scattering which takes place at the interface of the magnetic and non-magnetic layers and within the magnetic layers. Recorded data can be read from a magnetic medium because the external magnetic field from the recorded magnetic medium (the signal field) causes a change in direction of magnetization in the free layer, which in turn causes a change in resistance of the GMR sensor and a corresponding change in the sensed current or voltage.
- One or more merged heads may be employed in a magnetic disk drive for reading and writing information on circular tracks of a rotating disk. A merged head is mounted on a slider that is carried on a suspension. The suspension is mounted to an actuator which rotates the magnetic head to locations corresponding to desired tracks. As the disk rotates, an air layer (an “air bearing”) is generated between the rotating disk and an air bearing surface (ABS) of the slider. A force of the air bearing against the air bearing surface is opposed by an opposite loading force of the suspension, causing the magnetic head to be suspended a slight distance (flying height) from the surface of the disk.
- One important parameter of a magnetic head is its magnetic track width. If a magnetic head has a narrow track width, the tracks along a magnetic disk can also be made narrow. If the tracks on the disk can be made narrow, additional tracks can be formed on the disk to thereby increase its storage capacity. Thus, much emphasis has been placed on making the track widths of magnetic heads as small as possible. In turn, therefore, quick and accurate methods are needed to determine the magnetic widths of magnetic heads with narrow track width sizes. At the present state-of-the-art, magnetic track width sizes are less than 0.3 μm.
- Conventional methods for determining the magnetic track width are either (1) quick but inaccurate or (2) accurate but slow, particularly when dealing with magnetic heads having narrow track widths. One conventional method determines the magnetic track width from a full track profile of a magnetic track written on a disk. The full track profile consists of a plurality of signal amplitudes read by the magnetic head across a track of a magnetic disk at a plurality of head positions. The full track profile generally forms a bell-shaped curve when graphed (head position along x-axis, signal level along y-axis). The full track profile magnetic write width MWWFTP may be obtained based on the difference in left and right head positions which read half of the maximum head signal amplitude. Although this method can be performed relatively quickly, it is only accurate when MWW>>MRW (the magnetic read width) and when no side reading of the read sensor exists.
- The off-track reading capability (OTRC), which is a measure of how far the read head can go off track without picking up interference from adjacent tracks, and erase band width (EBW) can be found using the well-known “triple-track” method. In this method, a particular track is selected on a disk and two adjacent tracks which surround this track are written to. The middle track is then subsequently written to at a different frequency than the adjacent tracks for a partial erasure. Next, the full track profiles from the adjacent tracks are obtained. Best-fit lines are then fitted on the right side of the left adjacent track profile and on the left side of the right adjacent track profile. The two head positions where these best-fit lines intersect the x-axis are identified, and the difference between these positions is the OTRC. This method also suffers from inaccuracy due to side reading error.
- Another conventional method of determining the magnetic track width is the convolution method. In this method, the track width is determined by the convolution of the magnetic signal profile of the written track (assumed to be rectangular) and the micro-track width profile, based on
- FTP(x)=∫R(x−y)MG(y)dy=MTP(x−y)MG(y)dy,
- where R(x) is the reader response function, MG(x) is the magnetization of the data track, and FTP(x) and MTP(x) are the full and microtrack track profile, respectively. In this method, accurate results may be obtained despite the side-reading error. However, this method is too slow for use in production testing. Also, the off-track reading capability (OTRC) and erase band width (EBW) cannot be obtained using this method.
- Accordingly, what is needed is a quick and accurate method for determining the magnetic track width of a magnetic head, especially for magnetic heads having very narrow track widths.
- A quick and accurate method of determining the magnetic track width of a magnetic head is described herein. A full track profile of a magnetic track is obtained using the magnetic head. The full track profile includes a plurality of signal amplitudes read across a track of a magnetic disk at a plurality of magnetic head positions. Next, an initial track width value is determined from the full track profile data. Preferably, the initial value is the magnetic write width (MWWFTP) which is determined based on the difference in left and right head positions which read half of the maximum head signal level. This initial track width value is then adjusted with side reading correction values for determining the magnetic track width. The side reading correction values are based on an analysis of side reading “tails” of the bell-shaped signal curve that is formed by the track profile data when graphed.
- In one particular embodiment, the correction value for the left side reading tail (CSRL) is ΔYL/aL and the correction value for the right side reading tail (CSRR) is ΔYR/aR, respectively, such that the magnetic track width MWW=MWWFTP−CSRL−CSRR. The values aL and aR are slopes of best-fit lines fitted over left and right sides of the bell-shaped curve (YL=aL*Xoffset+bL and YR=aR*Xoffset+bR), respectively. The values ΔYL and ΔYR are obtained based on equations ΔYL=AL(SL)−(∂AL+∂AR)/2 and ΔYR=AR(SR)−(∂AL+∂AR)/2, respectively, where ∂AL=AL(SL)−AL(SL−X) and ∂AR=AR(SR)−AR(SR)−AR(SR+X); SL and SR are head offset positions that reflect where the best-fit lines and the side reading tails begin to deviate; AL and AR are signal amplitudes at specified head positions; and X=(MWWFTP−MRW)/2.
- For a fuller understanding of the nature and advantages of the present invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings:
- FIG. 1 is a schematic block diagram of a system for determining a magnetic track width of a magnetic head;
- FIG. 2A is an illustration of an ideal track profile of a magnetic head obtained from reading signal amplitudes measured at a plurality of magnetic head positions over a track of a magnetic disk;
- FIG. 2B is a graph showing a full track profile of a magnetic head, as well as equations for obtaining a magnetic track width from the full track profile;
- FIG. 3 is a graph showing the full track profile and a microtrack profile of the magnetic head;
- FIG. 4 is a graph of the microtrack profile of FIG. 3 at a smaller scaling;
- FIG. 5 is a flowchart which describes a method of determining a magnetic track width of a magnetic head in accordance with the present invention;
- FIG. 6 is a graph which shows side reading tail data of a full track profile;
- FIG. 7 is a graph which compares magnetic track widths obtained by the present invention and the measured physical track widths;
- FIG. 8 is a graph which compares magnetic track widths obtained by the present invention and theoretically calculated track widths;
- FIG. 9 is another graph which is the same as FIG. 8 except it uses micrometers (μm) instead of microinches (μin) for the units;
- FIG. 10 is a graph which shows full track profile data of two tracks which lie adjacent to and surround a middle track, used for determining an off-track read capability (OTRC) of a magnetic head;
- FIG. 11 is a graph which shows the full track profile data of FIG. 10, scaled up to show fuller views of the track profiles of the two tracks; and
- FIG. 12 is a graph which compares OTRCs obtained by the present invention and conventionally calculated OTRCs.
- The following description is the best embodiment presently contemplated for carrying out the present invention. This description is made for the purpose of illustrating the general principles of the present invention and is not meant to limit the inventive concepts claimed herein.
- A
system 100 for determining a magnetic track width of a magnetic head is shown in FIG. 1. Thesystem 100 in FIG. 1 includes acomputer 102, aspinstand 104, and a read/write analyzer 106.Computer 102 is coupled tospinstand 104 and read/write analyzer 106 through serial ports (not shown). Read/write analyzer 106 is also coupled tospinstand 104 through serial ports (not shown).Spinstand 104, which includes a replaceablemagnetic head 112 and a replaceablemagnetic disk 114, is basically a conventional disk drive device used for determining the magnetic track width of a magnetic head. Such aspinstand 104 may be obtained from, for example, Guzik Technical Enterprises of Mountain View, Calif., U.S.A. (e.g., Model # S-1701B). Read/write analyzer 106 is basically a conventional signal analyzer device which serves to measure, read, and write signals to and fromspinstand 104. These signals are converted from digital to analog (D/A) and analog to digital (A/D) as necessary. Such a read/write analyzer 106 may be obtained from, for example, Guzik Technical Enterprises of Mountain View, Calif., U.S.A. (e.g., Model # RWA-2585S PMRL 1G). -
Computer 102 may be a general purpose computer, such as a personal computer (PC), which includes one or more processors 108 (or controllers) andmemory 110.Memory 110 may be a disk, such as a hard disk, computer diskette, or compact disc (CD), or alternatively be memory of an integrated circuit (IC) device or processor which is a permanent part ofcomputer 102.Computer 102 includes software (i.e. computer instructions) which resides inmemory 110 and provides general control forsystem 100. For example, the software instructsspinstand 104 to movemagnetic head 112 to particular positions onmagnetic disk 114, write data todisk 114 at particular frequencies, and read data fromdisk 114. Given the appropriate track profile data, the computer instructions also perform calculations to determine the magnetic track width ofmagnetic head 112 in accordance with the present invention. The logic and calculations performed by the software are described below in detail. The software may be implemented in any suitable computer language, such as Visual Basic or Visual C++. - FIG. 2A is an illustrative example of an
ideal track profile 205 ofmagnetic head 112 of FIG. 1, where the write track width is made greater than the read track width.Ideal track profile 205 is obtained asmagnetic head 112 reads signal amplitudes across atrack 201 of a magnetic disk, which is illustrated by dashed-line representations ofmagnetic head 112 that extend from left to right in the figure.Track profile 205 is ideal in that it is not affected by any side reading from the magnetization of the positions that are not covered by the reader physically. Being ideal,track profile 205 is shown to have a short flat top and straight-lined sides with constant slopes. - As illustrated in FIG. 2A, the magnetic write width (w) is equal to the magnetic width of
track 201 whereas the magnetic read width (r) is equal to the width of a step function which represents an ideal reader response to magnetic fields. As indicated, the magnetic write width can be obtained by calculating the difference between the left and right head positions at half (½) of the maximum signal amplitude. Put another way, the magnetic write width from the full track profile (MWWFTP) can be found by identifying a maximum value in the plurality of signal amplitudes; identifying left and right side magnetic head positions XL1 and XR1 that correspond to half of the identified maximum value; and finding a difference ΔX1 between XL1 and XR1. On the other hand, the magnetic read width can be obtained by calculating the difference between the left and right head positions at zero signal amplitude (which is r+w), and then subtracting the magnetic write width from this value. Put another way, the magnetic read width from the full track profile (MRWFTP) can be found by identifying left and right side magnetic head positions XL2 and XR2 that correspond to a signal level of zero; finding a difference ΔX2 between XL2 and XR2 and finding a difference between ΔX2 and MWWFTP. - An ideal track profile, however, is difficult if not impossible to obtain. The full track profile is typically affected by side reading of the reader. This side reading error becomes relatively large percentage-wise when the write width becomes relatively small. FIG. 2B is a
graph 200 showing a more realisticfull track profile 202.Full track profile 202 consists of a plurality of signal amplitudes read across a track of a magnetic disk at a plurality of head positions. The plurality of signal amplitudes are represented along the y-axis in track average amplitude (TAA), and the plurality of head positions are represented along the x-axis in microinches (μin) as offsets from track center. - As shown in FIG. 2B, the data of full track profile forms a bell-shaped curve. Best-fit
straight lines side reading tail 212 exists to the left of best-fit line 204, and a rightside reading tail 214 exists to the right of best-fit line 205. Side reading tail data is hereby defined as that data that exist outside of the best-fit lines fitted along the left and right sides of the bell-shaped curve. These tails are caused by side reading which also widens the full track profile. Due to the side reading, the data and therefore the calculations for determining the magnetic write width described above in relation to FIG. 2A are not entirely accurate. The track width calculation error due to side reading becomes larger percentage-wise when the track width becomes smaller. - FIG. 5 is a flowchart which describes a method of determining a magnetic write width of a magnetic head in accordance with the present invention, which solves the problem of the prior art methods. This method is implemented in the system of FIG. 1 with software, which is stored in memory and executed by one or more processors. Referring back to the flowchart of FIG. 5, the track profile data for the magnetic head are obtained (step502). The track profile data include a plurality of signal amplitudes read across a track of a magnetic disk at a plurality of magnetic head positions. In this embodiment, the track profile data is the full track profile data of the magnetic head obtained from the read/write analyzer and spinstand of FIG. 1. The plurality of signal amplitudes of the full track profile form a bell-shaped signal curve when graphed over the plurality of magnetic head positions (e.g., see FIG. 2B).
- Next, an initial track width value is determined from the full track profile data using the conventional method (step504). In this embodiment, the initial track width value is the magnetic write width, referred to as MWWFTP, which is determined by the software from the full track profile. For example, MWWFTP may be obtained by identifying a maximum value in the plurality of signal amplitudes; identifying left and right side magnetic head positions XL1 and XR1 that correspond to half of the identified maximum value; and then finding a difference ΔX1 between XL1 and XR1. Thus, the relation may be represented as MWWFTP=(XR1−XL1).
- Correction values are then determined based on analyzing side reading tail data in the full track profile (step506). The analysis of side reading tails and the determination of correction values are described in a detailed analysis below. The initial track width value is adjusted with these correction values (step 508), and the final magnetic track width is obtained (step 510).
- To obtain the correction values, the magnetic read width from the full track profile (MRWFTP) is determined. The magnetic read width MRWFTP is found by first fitting left and right best-fit lines along left and right sides of the bell-shaped signal curve, respectively (see e.g., FIG. 2B). Once the best-fit lines are obtained, left and right side magnetic head positions XL2 and XR2 that correspond to a signal amplitude of zero along the left and right best-fit lines are identified. The difference ΔX2 between XL2 and XR2 is then found, and the MRWFTP is obtained by calculating the difference between ΔX2 and MWWFTP. The relation may be summarily represented as MRWFTP=(XR2−XL2)−MWWFTP=(XR2−XL2)−(XR1−XL1).
- To obtain the actual magnetic write width MWW, two correction values CSRL and CSRR are determined and used to adjust the initial track width value (here, MWWFTP). CSRL is the correction value for the left side reading tail and CSRR is the correction value for the right side reading tail. Once these correction values are obtained, the full track profile magnetic write width MWWFTP is adjusted based on the relation MWW=MWWFTP−CSRL−CSRR.
- FIG. 6 is a
graph 600 which shows side readingtail data 602 of a full track profile. Although only one side reading tail is shown for analysis (i.e., the left side reading tail), both left and right side reading tails are analyzed to obtain each correction value CSRL and CSRR. The correction values CSRL and CSRR are more specifically determined based on the relations CSRL=ΔYL/aL and CSRR=ΔYR/aR. Here, ΔYL=AL(SL)−(∂AL+∂AR)/2 and ΔYR=AR(SR)−(∂AL+∂AR)/2, where ∂AL=AL(SL)−AL(SL−X) and ∂AR=AR(SR)−AR(SR+X). AL and AR are signal amplitudes corresponding to particular magnetic head positions for the left and right side reading tails, respectively; aL and aR are slopes of the left and the right best-fit lines, respectively; and X=(MWWFTP−MRWFTP)/2. - In FIG. 6, best-
fit line 604 is shown fitted over the side readingtail data 602 and may represented by the equation YL=aL*Xoffset+bL. SL and SR are head positions that correspond to the point at which the left and right side reading tails of the bell-shaped curve begin to deviate from the left and the right best-fit lines, respectively. Since FIG. 6 shows the left side reading tail, a representative value of SL is shown. The signal amplitude value of AL(SL) is identified by an extendingline 606 which corresponds to head position SL, and the signal level value of AL(SL−X) is identified by an extendingline 608 which corresponds to head position (SL−X). Similar analysis of the right side reading tail (not shown in FIG. 6) determines the signal amplitude values of AR(SR) and AR(SR+X), using the best fit line represented by YR=aR*Xoffset+bR. - The above calculations used to find MWW can be quickly executed and the results are highly accurate. FIG. 7 is a
graph 700 which compares write widths obtained by the present invention and those that were actually measured physically with a critical dimension scanning electron microscope (CDSEM). A 45°line 702 shown in FIG. 7 represents the actual physical write width, which is typically smaller than the magnetic write width, such that measured track width data will generally lie above 45°line 702. Magnetic write width data is shown ingraph 700 as diamonds, two diamonds for each magnetic head. More particularly, conventionalwrite width data 704 from three wafers are denoted by hollow diamonds and shown generally above inventivewrite width data 710 which are from the same three wafers and denoted by solid diamonds. Astraight line 706 is fitted to conventionalwrite width data 704, and astraight line 712 is fitted to inventivewrite width data 710. Note that straight line 712 (invention) lies closer to and parallel with 45°line 702, which is desirable, whereas straight line 706 (conventional) lies further away from and not parallel with 450line 702.Straight lines line 702 and away from line 702 a distance of 0.08 and 0.04 nm, respectively. These two lines are used to identify how close the above two types of data are to the actual physical head write width. - To further illustrate the accuracy obtained, FIGS. 8 and 9 are
graphs Graphs graph 800 uses microinches (μin) whereasgraph 900 uses micrometers (μm). Theoretical magnetic write widths are graphed in FIG. 8 (clear diamonds) and acurve 802 was fitted to this data.Write width data 804 obtained by the present invention was also graphed in FIG. 8 (solid squares). Note how closely experimentalwrite width data 804 fits along theoreticalwrite width curve 802. The same data exists ingraph 900 of FIG. 9, which shows a theoreticalwrite width curve 902 and experimentalwrite width data 904 obtained by the present invention. - The off-track read capability (OTRC) for the magnetic head may also be obtained in a relatively accurate manner. FIGS. 10 and 11 show a graph1000 (smaller scale) and a graph 1100 (larger scale), respectively, which reveal the full track profile data of two tracks which lie adjacent to and surround a middle track. In accordance with a conventional method, a middle track is selected on the disk and two adjacent tracks which lie adjacent to this track are written to. The middle track is then subsequently written to at a different frequency than the adjacent tracks for a partial erasure. The full track profiles from the adjacent tracks are then obtained, shown as
track profile data fit lines adjacent track profile 1002 and on the left side of the rightadjacent track profile 1004, respectively. The two head positions where best-fit lines OTRC 1010 as indicated in FIG. 10. Side readingtail data 1012 are also shown in the figures. - As apparent from the figures, the side reading shifts
lines closer lines - As with the magnetic write widths, the OTRC obtained in accordance with the present invention is accurate. FIG. 12 is a graph which compares OTRCs obtained by the present invention and those obtained using the conventional method. The x-axis is the DWR in microinches (μin), and the y-axis is the OTRC in microinches (μin).
Conventional OTRC data 1206, shown as solid diamonds for each magnetic head, generally lies below a 45°line 1202 which results in abnormal negative EBW. Note also that some of theseconventional OTRC data 1206 have negative values, which is not physically possible. On the other hand,inventive OTRC data 1204, shown as hollow squares for each magnetic head, generally lies above 45°line 1202 as they should be. - Thus, a quick and accurate method of determining a magnetic track width of a magnetic head has been described. First, a full track profile for the magnetic head is obtained. This full track profile data includes a plurality of signal amplitudes read across a track of a magnetic disk at a plurality of magnetic head positions. Next, an initial write width value (having no side reading correction) is determined from the full track profile data. Preferably, the initial magnetic write width from the full track profile (MWWFTP) is determined based on the difference in left and right head positions which read half of the maximum head signal amplitude. The initial write width value is then adjusted with side reading correction values for determining the magnetic write width. The side reading correction values are based on an analysis of side reading “tails” of the bell-shaped signal curve that is formed by the full track profile data when graphed.
- In one particular embodiment, the correction value for the left side reading tail is ΔYL/aL and the correction value for the right side reading tail is ΔYR/aR, respectively, such that the magnetic write width MWW=MWWFTP−ΔYL/aL−ΔYR/aR. The values aL and aR are slopes of best-fit lines fitted over left and right sides of the bell-shaped curve (YL=aL*Xoffset+bL and YR=aR*Xoffset+bR), respectively. The values ΔYL and ΔYR are obtained based on equations ΔYL=AL(SL)−(∂AL+∂AR)/2 and ΔYR=AR(SR)−(∂AL+∂AR)/2, respectively, where ∂AL=AL(SL)−AL(SL−X) and ∂AR=AR(SR)−AR(SR+X); SL and SR are head offset positions that reflect where the best-fit lines and the side reading tails begin to deviate; AL and AR are signal amplitudes at specified head positions; and X=(MWWFTP−MRWFTP)/2.
- It is to be understood that the above is merely a description of preferred embodiments of the invention and that various changes, alterations, and variations may be made without departing from the true spirit and scope of the invention as set for in the appended claims. None of the terms or phrases in the specification and claims has been given any special particular meaning different from the plain language meaning to those skilled in the art, and therefore the specification is not to be used to define terms in an unduly narrow sense.
Claims (20)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/193,514 US6680609B1 (en) | 2002-07-11 | 2002-07-11 | Method and apparatus for determining the magnetic track width of a magnetic head |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/193,514 US6680609B1 (en) | 2002-07-11 | 2002-07-11 | Method and apparatus for determining the magnetic track width of a magnetic head |
Publications (2)
Publication Number | Publication Date |
---|---|
US20040010391A1 true US20040010391A1 (en) | 2004-01-15 |
US6680609B1 US6680609B1 (en) | 2004-01-20 |
Family
ID=30000038
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/193,514 Expired - Fee Related US6680609B1 (en) | 2002-07-11 | 2002-07-11 | Method and apparatus for determining the magnetic track width of a magnetic head |
Country Status (1)
Country | Link |
---|---|
US (1) | US6680609B1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20100061002A1 (en) * | 2008-02-28 | 2010-03-11 | Hitachi High-Technologies Corporation | Magnetic head inspection method, magnetic head inspection device, and magnetic head manufacturing method |
US7982989B1 (en) | 2009-12-23 | 2011-07-19 | Western Digital (Fremont), Llc | Method and system for measuring magnetic interference width |
US8625224B1 (en) | 2012-05-04 | 2014-01-07 | Western Digital (Fremont), Llc | Characterizing magnetic recording parameters of a disk drive by evaluating track profile of dual microtracks |
US8717695B1 (en) | 2012-02-29 | 2014-05-06 | Western Digital (Fremont), Llc | Characterizing head parameters of a disk drive by evaluating track profile of an overwritten track |
US8837065B1 (en) | 2013-08-09 | 2014-09-16 | WD Media, LLC | Systems and methods for fast measurement of channel performance metrics such as error margin and off-track recording capability in shingled magnetic recording |
Families Citing this family (21)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6860609B2 (en) * | 2001-12-26 | 2005-03-01 | Infocus Corporation | Image-rendering device |
US6842304B2 (en) * | 2003-01-08 | 2005-01-11 | International Business Machines Corporation | Measurement of write track width for magnetic tape head |
US7119537B2 (en) * | 2004-09-30 | 2006-10-10 | Hitachi Global Storage Technologies, Netherlands B.V. | Full track profile derivative method for read and write width measurements of magnetic recording head |
US7567397B2 (en) * | 2006-09-11 | 2009-07-28 | Hitachi Global Storage Technologies Netherlands B.V. | Adjacent Track Interference (ATI) identification methodology |
US7529050B2 (en) * | 2006-10-18 | 2009-05-05 | Hitachi Global Storage Technologies Netherlands B.V. | Track width measurement for magnetic recording heads |
US20080158705A1 (en) * | 2006-12-28 | 2008-07-03 | Xiaodong Che | Write head tester |
US7843658B2 (en) * | 2008-06-26 | 2010-11-30 | Tdk Corporation | Method for measuring magnetic write width in discrete track recording |
US7907361B2 (en) * | 2008-07-31 | 2011-03-15 | Hitachi Global Storage Technologies, Netherlands B.V. | Triple track test for side erase band width and side erase amplitude loss of a recording head |
US8102613B2 (en) * | 2009-09-25 | 2012-01-24 | Hitachi Global Storage Technologies Netherlands B.V. | System, method and apparatus for determining track pitch in a hard disk drive to satisfy the requirements of both off-track capacity and adjacent track erasure |
US8305705B1 (en) * | 2010-05-05 | 2012-11-06 | Western Digital Technologies, Inc. | Disk drive cross correlating track crossing signal with ideal signal to calibrate jog value |
US8395857B2 (en) | 2010-11-08 | 2013-03-12 | HGST Netherlands B.V. | Simulating discrete track media with continuous media for head evaluation |
US8699172B1 (en) | 2011-02-16 | 2014-04-15 | Western Digital Technologies, Inc. | Disk drive generating off-track read capability for a plurality of track segments |
US8885283B1 (en) | 2011-11-03 | 2014-11-11 | Western Digital Technologies, Inc. | Disk drive adjusting write block size based on detected vibration |
US8711506B1 (en) | 2012-05-31 | 2014-04-29 | Western Digital Technologies, Inc. | Disk drive increasing capacity by adjusting a servo gate during write operations |
US8773958B2 (en) | 2012-08-07 | 2014-07-08 | Tdk Corporation | Estimation method of Curie temperature distribution width |
US8614934B1 (en) | 2012-08-10 | 2013-12-24 | Tdk Corporation | Method for characterization evaluation of thermally-assisted magnetic recording device |
US8891192B1 (en) | 2012-11-15 | 2014-11-18 | Western Digital Technologies, Inc. | Disk drive calibrating parameter by injecting noise signal and measuring off-track read capability |
US9047919B1 (en) | 2013-03-12 | 2015-06-02 | Western Digitial Technologies, Inc. | Disk drive initializing servo read channel by reading data preceding servo preamble during access operation |
US8908310B1 (en) | 2013-07-11 | 2014-12-09 | Western Digital Technologies, Inc. | Adaptive shingle guard band |
US9082458B1 (en) | 2014-03-10 | 2015-07-14 | Western Digital Technologies, Inc. | Data storage device balancing and maximizing quality metric when configuring arial density of each disk surface |
US9053712B1 (en) | 2014-05-07 | 2015-06-09 | Western Digital Technologies, Inc. | Data storage device reading servo sector while writing data sector |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS59180820A (en) | 1983-03-31 | 1984-10-15 | Toshiba Corp | Measuring circuit for characteristics of magnetic head |
US6091559A (en) | 1994-12-19 | 2000-07-18 | Mobile Storage Technology Inc. | Variable zone layout and track pitch parameter considerations for information storage disk drive |
JP3368788B2 (en) | 1997-02-17 | 2003-01-20 | ティーディーケイ株式会社 | Inspection method and inspection apparatus for magnetic head having spin valve magnetoresistive element |
US6265868B1 (en) | 1997-12-11 | 2001-07-24 | Seagate Technology Llc | System and method for measuring total track width of a test track in magnetic media |
US6249890B1 (en) | 1998-06-05 | 2001-06-19 | Seagate Technology Llc | Detecting head readback response degradation in a disc drive |
JP3757071B2 (en) * | 1999-01-21 | 2006-03-22 | 株式会社日立グローバルストレージテクノロジーズ | Magnetic disk unit |
-
2002
- 2002-07-11 US US10/193,514 patent/US6680609B1/en not_active Expired - Fee Related
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20100061002A1 (en) * | 2008-02-28 | 2010-03-11 | Hitachi High-Technologies Corporation | Magnetic head inspection method, magnetic head inspection device, and magnetic head manufacturing method |
US8278917B2 (en) * | 2008-02-28 | 2012-10-02 | Hitachi High-Technologies Corporation | Magnetic head inspection method and magnetic head inspection device |
US7982989B1 (en) | 2009-12-23 | 2011-07-19 | Western Digital (Fremont), Llc | Method and system for measuring magnetic interference width |
US8717695B1 (en) | 2012-02-29 | 2014-05-06 | Western Digital (Fremont), Llc | Characterizing head parameters of a disk drive by evaluating track profile of an overwritten track |
US8625224B1 (en) | 2012-05-04 | 2014-01-07 | Western Digital (Fremont), Llc | Characterizing magnetic recording parameters of a disk drive by evaluating track profile of dual microtracks |
US8837065B1 (en) | 2013-08-09 | 2014-09-16 | WD Media, LLC | Systems and methods for fast measurement of channel performance metrics such as error margin and off-track recording capability in shingled magnetic recording |
Also Published As
Publication number | Publication date |
---|---|
US6680609B1 (en) | 2004-01-20 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6680609B1 (en) | Method and apparatus for determining the magnetic track width of a magnetic head | |
Tsang et al. | Gigabit density recording using dual-element MR/inductive heads on thin-film disks | |
US6724583B2 (en) | Adjustable permanent magnet bias | |
US7428126B2 (en) | Domain wall free shields of MR sensors | |
US9548083B2 (en) | Read sensor testing using thermal magnetic fluctuation noise spectra | |
US7633694B2 (en) | Method and apparatus for quantifying stress and damage in magnetic heads | |
US20090323209A1 (en) | Method for measuring magnetic write width in discrete track recording | |
US7119537B2 (en) | Full track profile derivative method for read and write width measurements of magnetic recording head | |
JP3075253B2 (en) | Spin valve type magnetic sensing element, magnetic head using the same, and magnetic disk drive | |
US8225486B2 (en) | Method of manufacturing a perpendicular magnetic recording head | |
US9245550B2 (en) | Write head tester using inductance | |
US7411754B2 (en) | System and method for measuring readback signal amplitude asymmetry in a perpendicular magnetic recording disk drive | |
US20080061773A1 (en) | Method of evaluating a magnetoresistance effect read head | |
US20040041559A1 (en) | Cross talk bit error rate testing of a magnetic head | |
JP3439693B2 (en) | Measurement method and inspection method of track pitch of magnetic head, and measurement device and inspection device | |
US20060221508A1 (en) | GMR spin-valve element evaluation method, magnetic head manufacturing method, and magnetic storage device | |
JP3717628B2 (en) | Method and apparatus for evaluating magnetoresistive head | |
US6489762B2 (en) | Method to detect junction induced signal instability from GMR/MR heads | |
JP3016368B2 (en) | Recording magnetization state measurement device | |
US6504362B2 (en) | Process of measuring slide-reading of abutted-junction read heads | |
JP3828662B2 (en) | Signal defect inspection method for magnetic disk | |
KR100440794B1 (en) | Method for discerning damage of a magnetoresistive head by measuring resistance of a magnetoresistive sensor of the magnetoresistive head | |
Dee | Comparison of MR and GMR spin-valve heads for magnetic recording on MP tape | |
Hu et al. | Comparative study of head-disk spacing measurement techniques between optical method and various in-situ methods | |
JP2005018826A (en) | Inspection method for vertical magnetic recording disk and hard disk drive |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: INTERNATIONAL BUSINESS MACHINES CORPORATION, NEW Y Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:FANG, PETER CHENG-I;LAM, TERENCE TIN-LOK;LIN, ZHONG-HENG;REEL/FRAME:013097/0812;SIGNING DATES FROM 20020530 TO 20020621 |
|
FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
CC | Certificate of correction | ||
AS | Assignment |
Owner name: HITACHI GLOBAL STORAGE TECHNOLOGIES NETHERLANDS B. Free format text: CHANGE OF NAME;ASSIGNOR:MARIANA HDD B.V.;REEL/FRAME:015348/0191 Effective date: 20021231 Owner name: MARIANA HDD B.V., NETHERLANDS Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:INTERNATIONAL BUSINESS MACHINES CORPORATION;REEL/FRAME:015370/0450 Effective date: 20021231 |
|
FEPP | Fee payment procedure |
Free format text: PAYER NUMBER DE-ASSIGNED (ORIGINAL EVENT CODE: RMPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
REMI | Maintenance fee reminder mailed | ||
LAPS | Lapse for failure to pay maintenance fees | ||
STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |
|
FP | Lapsed due to failure to pay maintenance fee |
Effective date: 20120120 |