JP2004326865A - Magnetic disk device having outer magnetic field detecting function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic disk device which detects the outer magnetic field applied to a head in a simple constitution without providing another circuit for detecting the outer magnetic field and can prevent the outer magnetic impairment based on this detected result. <P>SOLUTION: This magnetic disk device having an outer magnetic field detecting function has a control means in which a magnetoresistive effect of which the operation region is non-linear in the outside magnetic field being a magnetic field or less at which a recording head is damaged is used for a reproducing head, detects the outer magnetic field applied to the device from the quantity of the outer magnetic field distortion of the magnetoresistive effect element of this reproducing head, when the detected outer magnetic field is the prescribed value or more, and the outer magnetic field impairment avoiding operation such as prohibition of writing of the head for the device, evacuation to the outside of the magnetic disk medium is performed, or the like is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic disk drive having an external magnetic field detection function for avoiding disturbance due to a disturbance magnetic field.
[0002]
[Prior art]
2. Description of the Related Art In recent years, various types of information devices have become more portable due to the reduction in size and weight of magnetic disk devices, and magnetic disk devices have been increasingly exposed to more severe magnetic field environments. When a magnetic disk device receives a magnetic field from the outside, stray magnetic flux concentrates on the recording head, so that the following data erasure failure or recording failure occurs.
[0003]
For example, if the stray magnetic flux is excessively concentrated on the recording magnetic pole of the recording head, the magnetic field leaking from the tip of the magnetic pole onto the recording medium will destroy the recording data on the medium. In this case, since all the magnetization information immediately below the recording magnetic pole may destroy not only user data but also servo data describing the position information of the head, the head cannot be positioned on the recording medium and the data is destroyed. It is possible to run away while running. In the worst case, it is assumed that most data on the recording medium is destroyed.
[0004]
On the other hand, even at a slight magnetic field intensity, when the recording operation is performed, when the final recording (magnetization) direction of the recording magnetic pole and the external magnetic field direction match, residual magnetization occurs in the recording magnetic pole, which may cause data destruction. There is.
[0005]
In addition, even if data destruction does not occur, the external magnetic field during recording changes the distribution of the recording magnetic field applied from the tip of the recording pole to the recording medium, so that the magnetization transition position to be recorded shifts to a desired position. Recording distortion occurs, and the problem that the error rate deteriorates is likely to occur.
[0006]
For the above reasons, it is considered useful to establish an external magnetic field detecting means in the magnetic disk drive. In particular, the perpendicular recording type magnetic disk drive, which is currently being developed by various companies for higher recording density, has excellent recording performance, but the above-mentioned obstacles due to the external magnetic field appear more remarkably than the current longitudinal recording method. Therefore, highly accurate external magnetic field detecting means and strong obstacle avoiding means have become necessary.
[0007]
However, there is a problem that a new circuit is required for detecting the external magnetic field, the configuration becomes complicated, and it is difficult to accurately detect a disturbance magnetic field concentrated on the head.
As a prior art relating to the detection of the external magnetic field and the compensation of the magnetization transition, there is a technique disclosed in JP-A-2000-207704. In this method, a magnetization reversal position by an adjacent bit pattern is predicted in advance in a recording signal sequence, and recording compensation is performed by leading or delaying a magnetization reversal timing in accordance with the adjacent bit pattern.
[0008]
[Patent Document 1]
JP 2000-207704 A (Summary, FIG. 6)
[0009]
[Problems to be solved by the invention]
However, in the above technique, it is necessary to provide a recording compensation circuit for a disturbance magnetic field, which causes a problem in terms of cost.
In a perpendicular magnetic recording type magnetic disk drive, if the device receives a disturbing magnetic field and the stray magnetic flux concentrates on the recording magnetic pole, the magnetic transition of the recording magnetic pole changes and the magnetization transition position shifts from the normal position. The problem of worsening the error example is not solved.
[0010]
Therefore, in the present invention, the disturbance magnetic field information is obtained from the compensation amount of the reproduction waveform by using the MR element having a narrow dynamic range in which the reproduction waveform distortion is generated by the disturbance magnetic field and the reproduction distortion compensation circuit. The reproduction waveform distortion compensation circuit can adaptively change the compensation amount so as to optimize the error rate, so by monitoring the fluctuation value of the compensation amount, the external magnetic field applied to the head can be easily detected without impairing the format efficiency. can do. Further, since it is premised that a reproduced waveform distortion is caused by an external magnetic field, the present invention can be applied to both perpendicular recording and in-plane recording. Furthermore, based on the obtained fluctuation amount of the compensation amount of reproduction distortion, it is possible to avoid the above-mentioned obstacles due to various disturbance magnetic fields by applying head retraction, recording operation prohibition, and recording distortion compensation.
[0011]
That is, the present invention uses a reproducing head using a magnetoresistive element having a narrow dynamic range in which a reproducing waveform is distorted by an external magnetic field and a reproducing waveform compensating circuit for compensating for the reproducing waveform distortion. It is an object of the present invention to provide a magnetic disk drive capable of detecting an external magnetic field and avoiding an external magnetic field failure.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a disk drive according to the present invention includes a magnetic recording medium, a recording head that records information on the magnetic recording medium, and reproduces information on the magnetic recording medium, A magnetic head comprising a magnetoresistive element having an MR operation region that is non-linear due to the following external magnetic field that causes a failure of the recording head; and a magnetic head composed of a reproducing head including the magnetoresistive element. External magnetic field detecting means for detecting an external magnetic field, external magnetic field obstacle avoiding means for avoiding an obstacle to the external magnetic field, and obstacles caused by the external magnetic field are avoided by the external magnetic field detecting means and the external magnetic field obstacle avoiding means. And control means for performing such control.
[0013]
As described above, it is possible to provide a magnetic disk drive capable of effectively detecting a magnetic field and avoiding a magnetic field failure by using a head having a narrow dynamic range.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a hard disk drive which is a magnetic disk device as a disk device will be described in detail with reference to the drawings.
<Configuration of this embodiment>
FIG. 1 is a block diagram showing a main part of a magnetic disk device as one of the disk drives according to the embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a magnetic disk device, and 2 denotes a host system such as a PC on which the magnetic disk device 1 is mounted. The host system 2 is connected via a host interface of the magnetic disk device 1.
[0015]
The magnetic disk device 1 includes a magnetic disk 3 as a recording medium for recording data. The magnetic disk 3 is driven to rotate by a spindle motor (SPM) 5.
[0016]
A plurality of concentric tracks are formed on each data surface of the magnetic disk 3, and a plurality of servo areas in which servo data used for positioning control and the like are recorded are arranged at equal intervals on each track. A data area is provided between the servo areas, and a plurality of data sectors are set in the data area. In addition, a strong magnetic field detecting track 3a is provided on a predetermined area (near the outermost periphery of the magnetic disk 3 in this embodiment) on the magnetic disk 3. The details of the strong magnetic field detection track 3a will be described later.
[0017]
On each data surface of the magnetic disk 3, a read / write combined head 4 used for writing data to the magnetic disk 3 and reading data from the magnetic disk 3 is provided. The head 4 is mounted on a slider that flies above the rotating magnetic disk 3, and is driven by a voice coil motor (VCM) 7 as a slider moving mechanism so as to be movable in the radial direction of the magnetic disk 3. A seek and positioning are performed at a target position, that is, a target track.
[0018]
A ramp 16 is provided outside the magnetic disk 3 near the outer periphery of the magnetic disk 3 so as to allow the head 4 to retreat from the magnetic disk 3 when the read / write operation of the head 4 is stopped. It is provided to stop at.
[0019]
In the present embodiment, a perpendicular magnetic recording system in which the recording layer of the magnetic disk 3 is magnetized in the vertical direction is used, and the head 4 and the magnetic disk 3 have a configuration suitable for this. FIG. 2 shows the structure of the head 4 and the magnetic disk 3 of this embodiment.
[0020]
In the present embodiment, the read head 42 is a so-called MR head using a magneto-resistance effect element (hereinafter, referred to as an MR element 44), and an inductive head is used as the write head 43.
[0021]
The head 4 is provided with a read head 42 on the side of the slider body 41 (B direction in FIG. 2), which is a leading edge, and a write head 43 on the rear side (A direction in FIG. 2). In the read head 42, the MR element 44 serving as a magnetic sensing portion made of a single layer having a magnetoresistive effect or a plurality of layers of magnetic thin films is sandwiched between a pair of shield cores, that is, an upper shield core 45 and a lower shield core 46, and has a predetermined magnetic field. Are arranged in a space forming a gap.
[0022]
The write head 43 has a structure as an inductive head including an upper magnetic pole 47, a coil 48, and a lower magnetic pole 49. The tips of the magnetic poles 47 and 49 have a structure peculiar to the perpendicular magnetic recording system. The upper magnetic pole 47 is called a main magnetic pole, and the lower magnetic pole 49 is called an auxiliary magnetic pole. The magnetic layer 30 of the magnetic disk 3 is magnetized. The auxiliary magnetic pole 49 pulls up the magnetic flux flowing from the main magnetic pole 47 into the magnetic layer 30 of the magnetic disk 3 as a magnetic recording medium and the soft magnetic layer 31 provided thereunder to form a magnetic path.
[0023]
A magnetic disk 3 as a magnetic recording medium has a magnetic layer 30 having a magnetic anisotropy in a vertical direction and having a function as a recording layer, and a soft magnetic layer 31 between the magnetic layer 30 and the substrate 33. Consists of a structure. The soft magnetic layer 31 draws a magnetic flux generated from the main magnetic pole 47 in the vertical direction, and magnetizes the magnetic layer 30 as a recording layer sandwiched between the main magnetic pole 47 and the soft magnetic layer 31 in a direction perpendicular to the surface direction of the magnetic disk. Play an auxiliary role. The magnetic flux flowing into the soft magnetic layer 31 passes through the soft magnetic layer 31 in the in-plane direction of the magnetic disk and returns to the auxiliary magnetic pole 49. That is, the magnetic flux generated from the main magnetic pole 47 forms a magnetic flux path of the magnetic layer 30 → the soft magnetic layer 31 → (recording layer 30) → the auxiliary magnetic pole 49.
[0024]
Returning to FIG. 1 again, the head 4 is connected to the head amplifier circuit 8. The head amplifier circuit 8 controls input / output of a read / write signal to / from the head 4. The head amplifier circuit 8 switches the read head 42 and supplies a sense current. It has a read amplifier circuit 81 for amplifying and a write amplifier 80 for supplying a write current to the write head 43 in synchronization with a write signal from a write channel 90 to be described later. These functions are in accordance with instructions from the CPU 12 to be described later. .
[0025]
The head amplifier circuit 8 is connected to the read / write circuit 9. The read / write circuit 9 receives a read signal from the head 4 amplified by the read amplifier 81 of the head amplifier circuit 8 and performs a signal processing necessary for a data reproducing operation. And a write channel 90 connected to the encoding circuit 902 and having a recording compensation circuit 901 having a function of delaying or leading a signal inversion position from a normal position. The read / write circuit 9 also has a signal processing function of performing processing for extracting servo data necessary for servo processing such as head positioning control.
[0026]
The read / write circuit 9 is connected to the HDC 10, the servo controller 11, and the CPU 12. The HDC 10 forms an interface with the host system 2, controls communication of commands and data with the host system 2, and performs data communication with the magnetic disk 3 via the read / write circuit 9. Control.
[0027]
The servo controller 11 receives the data reproduced by the read / write circuit 90 and executes signal processing necessary for servo processing. In other words, the servo controller 11 has a timing generation function of reproducing various timing signals such as servo gates that are valid only during the servo area from the data reproduced by the read / write circuit 9, and the servo data in the servo area recorded in the servo area. It has a decoding function to extract and decode cylinder codes.
[0028]
The CPU 12 forms a main control device that controls each unit in the magnetic disk device 1 according to a control program stored in the ROM 15. In other words, the CPU 12 seeks to move the head 4 to the target position in accordance with the cylinder code in the servo data extracted by the servo controller 11 and the burst data in the servo data extracted by the read / write circuit 9. A well-known control process such as positioning control and HDC 10 control is performed.
[0029]
The CPU 12 includes a ROM 15 that stores a control program for controlling each unit in the magnetic disk device 1, a RAM 14 that provides a work area for the CPU 12, and a parameter for controlling the magnetic disk device 1. A rewritable flash ROM (FROM) 13 used for storage and the like is connected.
[0030]
Next, details of the external magnetic field detecting means in the present embodiment will be described below.
First, the read head 42 according to the present embodiment is characterized in that the reproduced waveform is distorted by a weaker magnetic field that causes an obstacle such as information destruction due to an external magnetic field. The operation principle will be described with reference to FIGS.
[0031]
FIG. 3 is a so-called ρH curve in which the horizontal axis indicates the magnetic field strength (H) related to the MR element 44 and the vertical axis indicates the resistance (ρ) of the MR element 44. FIG. The relationship between the input magnetic field and the output signal is also shown. The input magnetic field (a) is a medium magnetic field, that is, a magnetic field of data recorded on the magnetic disk 3, and the vertical axis represents time. As shown in FIG. 3, since the MR resistance of the MR element 44 changes almost linearly with respect to the input magnetic field, the output signal, that is, the change output signal of the MR resistance is as shown in FIG.
[0032]
On the other hand, FIG. 4 shows a case where a disturbing magnetic field is applied to the magnetic disk drive 1. The input magnetic field (a ′) is displaced by the disturbing magnetic field to the medium magnetic field (the offset (e) is applied). The operating region deviates from the linear part. As a result, waveform distortion (asymmetry) occurs in the reproduced waveform as shown in (b '), and the error rate of the reproduced data is degraded. This deterioration of the error rate can be mitigated by a reproduction distortion compensation circuit 911 described later.
[0033]
In this case, the distortion of the ρH curve causes distortion of the reproduced waveform in the absence of a disturbing magnetic field, but there is no problem in detecting the disturbing magnetic field. Rather, since the reproduction distortion fluctuates even with a weak magnetic field, the sensitivity of the disturbance magnetic field detection increases.
[0034]
The read channel 91 in the present embodiment includes a reproduction distortion compensation circuit 911 for compensating for asymmetric distortion of a reproduction waveform, and a waveform equalization circuit 912 for shaping a desired waveform by various signal processing. In the reproduction distortion compensation circuit 911, the compensation amount is adaptively adjusted so that the error rate of the reproduction data is optimized. The flash ROM (FROM) 13 has a memory circuit as an initial compensation amount in the absence of a disturbing magnetic field and a predetermined amount of compensation amount fluctuation as a criterion for executing an external magnetic field obstacle avoidance operation to be described later. It is assumed that it is stored at the manufacturing stage.
[0035]
FIG. 5 shows the variation in the error rate of the reproduced data when a disturbance magnetic field is applied during the reproduction. In the graph, the horizontal axis is the external magnetic field (Oe), and the vertical axis is the error rate (Log).
BER). FIG. 5A shows a case where the reproduction distortion compensating circuit 911 is not used. When an external magnetic field is applied, reproduction distortion occurs and the error rate deteriorates. On the other hand, FIG. 7B shows a case where the reproduction distortion compensation circuit 911 of the present embodiment is used, and the error rate is less deteriorated than when the reproduction distortion compensation circuit 911 is not used. At that time, the reproduction distortion compensation amount fluctuates one-to-one with respect to the external magnetic field as shown in FIG.
[0036]
In the combination of the head 4 and the magnetic disk 3 according to the present embodiment, data destruction due to residual magnetization after recording occurs in FIG. 6A and data destruction occurs due to magnetic flux concentration in FIG. In addition, each of the avoiding operations can be performed.
[0037]
As described above, the present embodiment is characterized in that reproduction distortion due to an external magnetic field occurs before various external magnetic field disturbances due to the recording head occur. And adjusting the recording head (data destruction) characteristics.
[0038]
<Operation to avoid data destruction due to residual magnetization after recording>
FIG. 7 is a block diagram showing an operation of avoiding data destruction due to residual magnetization after recording. When the HDC 10 receives a write command as a write command from the host system 2 (S71), first, the head 4 seeks the head 4 to a target track in order to execute a data write operation on the magnetic disk 3.
[0039]
Next, a dummy read (magnetic field detection lead) for detecting an external magnetic field (S73) is executed. When an external magnetic field is detected by this magnetic field detection lead, that is, when the magnetic disk device 1 receives an external magnetic field, the reproduction distortion compensation circuit 911 adjusts the compensation amount to optimize the error rate of the reproduction data. . At the time of the magnetic field detection read, the reproduction data is not transferred to the host system 2.
[0040]
Next, the CPU 12 acquires a distortion compensation amount from the flash ROM (FROM) 13 from the reproduction distortion compensation circuit 911 (S74), and obtains a difference between the initial compensation amount acquired from the flash ROM (FROM) 13 and the current compensation amount. (Compensation amount fluctuation amount) is calculated, and it is determined whether or not the amount exceeds a predetermined amount that prohibits the write operation (S75).
[0041]
Here, the predetermined amount needs to be equal to or less than a magnetic field at which data is destroyed due to residual magnetization after recording. In the present embodiment, A in FIG. 6 corresponds to this. The predetermined amount is stored in a flash ROM (FROM) 13 in the magnetic disk device 1 in advance when the magnetic disk device 1 is manufactured. If the amount of change in the compensation amount is equal to or less than the predetermined amount, a data write operation is executed (S76). If the amount of change in the compensation amount exceeds the predetermined amount, the data is erased due to the residual magnetization of the recording magnetic pole in the write operation. It is determined that there is a danger, and a write error due to a magnetic field detection abnormality is transmitted to the host system 2 and notified (S77). In this case, the CPU 12 repeatedly executes the magnetic field detection read until the external magnetic field around the magnetic disk device 1 is released and the write is executed or the write stop command is issued from the host system 2.
[0042]
<Recording compensation for recording distortion due to external magnetic field>
If the compensation amount fluctuation does not exceed the predetermined amount (A in FIG. 6 in this embodiment) stored in the above-mentioned flash ROM (FROM) 13, the write operation (S76) of the flowchart shown in FIG. 7 is executed. You. In this case, data erasure does not occur, but recording distortion occurs due to a change in the recording magnetic field distribution due to the concentration of the stray magnetic field on the recording magnetic pole. Then, it is possible to apply the magnetic field detecting means in the present embodiment. In this case, the recording compensation circuit 901 performs recording compensation with reference to a recording compensation amount table corresponding to the compensation amount variation stored in the flash ROM (FROM) 13.
[0043]
<Operation to avoid data destruction due to concentration of floating magnetic flux on magnetic pole>
If the distortion compensation amount exceeds B in FIG. 6, there is a danger of data destruction due to the concentration of the stray magnetic field on the recording magnetic pole. Therefore, the data destruction avoidance operation in the present embodiment will be described with reference to the block diagram shown in FIG.
[0044]
When the head 4 is loading on the magnetic disk 3 such as during reading or standby, the CPU 12 periodically executes a magnetic field detection lead (S81) for detecting an external magnetic field. At this time, the magnetic field detection read operation (S81) may use any sector on the magnetic disk 3.
[0045]
The CPU 12 obtains the distortion compensation amount by the reproduction distortion compensation circuit 911 (S82), and determines whether or not the compensation amount fluctuation amount exceeds a predetermined amount (B in FIG. 6 in the present embodiment) (S83). .
[0046]
The predetermined amount is stored in the flash ROM (FROM) 13 in advance at the time of manufacturing the magnetic disk device 1. The CPU 12 continuously monitors the distortion compensation amount and the distortion compensation fluctuation amount when the compensation amount fluctuation amount is equal to or less than the predetermined amount, but notifies the error occurrence due to the concentration of the stray magnetic flux to the magnetic pole when the compensation amount fluctuation amount exceeds the predetermined amount. (S86). At this time, the head 4 may be retracted to a strong magnetic field detection track 3a provided on the magnetic disk 3 described later, or may be a ramp 16 which is a head retracting member provided outside the magnetic disk 3.
[0047]
When the save destination is the strong magnetic field detection track 3a, the magnetic field detection read is repeatedly performed on the strong magnetic field detection track 3a until the distortion compensation amount becomes equal to or less than the predetermined amount and the escape is canceled (S87).
[0048]
On the other hand, when the evacuation destination is the ramp 16 which is the head evacuation member, for example, the head 4 is periodically loaded on the magnetic field detection read track 3a provided near the outermost periphery of the magnetic disk 3, and the magnetic field detection read is executed. Is done.
[0049]
<Explanation of strong magnetic field detection truck>
The above-described strong magnetic field detection track 3a will be described in detail below.
When the head 4 is positioned on the magnetic disk 3 in a strong magnetic field exceeding (b) of FIG. 6, there is a high risk of destroying data which is magnetization information already recorded on the magnetic disk 3. When the head 4 leaves the magnetic disk 3 and retreats on the ramp 16 as a magnetic head retreat member, the above-described magnetic field detection lead cannot be performed. Therefore, in the present embodiment, the strong magnetic field detecting track 3a for detecting the strong magnetic field which does not hinder the data destruction due to the magnetic flux concentration on the recording magnetic pole 43 is provided at a predetermined position of the magnetic disk 3, for example, near the outermost periphery. ing.
[0050]
In the present embodiment, the movement of the head 4 is performed by rotary driving (not a linear actuator) by a voice coil motor (VCM) 7 which is a slider moving mechanism. A skew angle occurs, which is different. Further, the read head 42 is disposed closer to the leading edge than the write head 43, that is, closer to the rotation axis. That is, geometrically, the recording magnetic pole 47 is located on the outer track with respect to the read head 42 on the outer peripheral side of the magnetic disk 3, while it is located on the inner track on the inner peripheral side.
[0051]
In particular, when the radial distance (A in FIG. 9) between the read head 42 and the recording magnetic pole 47 is equal to or longer than one track interval (Tp in FIG. 9), the recording magnetic pole 47 between the read head 42 and the write head 42 becomes Since they are located on different tracks, even if a strong magnetic field is applied, data immediately below the read head 42 can be continued on track without being destroyed.
[0052]
When the read head 42 is on-track to a track near the outermost periphery, the recording magnetic pole 47 of the write head 42 is further positioned on the outer peripheral side, that is, on a track where no data exists, so that a failure due to data destruction by the recording magnetic pole 47 occurs. do not do. Therefore, in the present embodiment, the outermost track is provided with the strong magnetic field detection track 3a as a retreat destination of the head 4 capable of detecting the strong magnetic field.
[0053]
Since the same condition is satisfied for the track near the innermost circumference, the strong magnetic field detection track 3a may be provided in the track near the innermost circumference. However, in an emergency due to a disturbance other than an external magnetic field such as an impact, the head 4 is moved to the magnetic disk medium. Since it is possible to retreat to the lamp 16 which is a head retreating member without passing over the upper part 3, it is desirable that the strong magnetic field detecting track 3a is near the outermost periphery.
[0054]
If the radial distance (A in FIG. 9) between the track to be read and the recording magnetic pole 47 (A in FIG. 9) is not less than the innermost circumference and the outermost circumference, one or two destructible tracks are provided. Thus, strong magnetic field information can be obtained without destroying data on the magnetic disk medium 3 immediately below the read head 42.
[0055]
<Modification of Embodiment>
In a modification of the above-described embodiment, the read head 42 is configured such that the positioning accuracy is deteriorated before the above-described data destruction failure occurs due to reproduction distortion due to a disturbance magnetic field. The read channel 91 is provided with a circuit for detecting the positioning accuracy of the head 4 (not shown), and monitors the positioning accuracy when the head 4 is on the magnetic disk 3.
[0056]
FIG. 10 shows the relationship between the disturbance magnetic field and the positioning accuracy in a modification of the present embodiment. As shown in the figure, the positioning accuracy deteriorates with the increase of the disturbance magnetic field, so by monitoring this positioning accuracy, the data destruction due to the residual magnetization of the recording magnetic pole and the magnetic flux concentration on the recording magnetic pole An avoidance operation can be performed for data destruction. Each avoiding means can use the same method as in the above-described embodiment.
[0057]
Various data destruction could not be avoided because it occurred before the positioning system deteriorated.However, since the positioning deteriorated before the data destruction due to the above configuration, the occurrence of disturbance magnetic field was detected by monitoring this. And can easily avoid data corruption that can be caused by this.
[0058]
【The invention's effect】
As described in detail above, according to the present invention, by using a reproducing head using a magnetoresistive element having a narrow dynamic range in which a reproduction waveform is distorted by an external magnetic field, and a reproduction distortion compensation circuit for compensating for reproduction waveform distortion, With a simple configuration, it is possible to provide a magnetic disk drive capable of detecting an external magnetic field applied to a head from the periphery of the device and avoiding an external magnetic field failure, and a method of detecting the external magnetic field of the device.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a magnetic disk drive according to an embodiment of the present invention.
FIG. 2 is a sectional view showing the structure of a single-pole head and a two-layer film recording medium according to an embodiment of the present invention.
FIG. 3 is a graph showing a relationship between a ρH curve, an input magnetic field, and an output signal of the reproducing head according to the embodiment of the present invention (with no disturbance magnetic field).
FIG. 4 is a graph (with a disturbance magnetic field) showing a relationship between a ρH curve, an input magnetic field, and an output signal of the reproducing head according to the embodiment of the present invention.
FIG. 5 is a graph showing an error rate variation of reproduced data due to a disturbance magnetic field according to the embodiment of the present invention.
FIG. 6 is a graph showing a relationship between a disturbance magnetic field and a reproduction distortion compensation amount according to the embodiment of the present invention.
FIG. 7 is a flowchart showing an operation for avoiding data destruction due to residual magnetization after recording according to the embodiment of the present invention.
FIG. 8 is a flowchart showing an operation for avoiding data destruction due to magnetic flux concentration on a recording magnetic pole according to the embodiment of the present invention.
FIG. 9 is a view for explaining a strong magnetic field detection track according to the embodiment of the present invention.
FIG. 10 is a graph showing a relationship between a disturbance magnetic field and head positioning accuracy according to the embodiment of the present invention.
[Explanation of symbols]
1. Magnetic disk drive
2. Host system
3. Magnetic disk media
30 ... magnetic layer (recording layer)
31 Soft magnetic layer
32 ... board
3a: Track for strong magnetic field detection
4 Head
41 ... Slider body
42 Readhead
43 …… Light head
44 …… MR element
45 …… Upper shield core
46 …… Lower shield core
47 ... Main pole
48 ... Coil
49 ... Lower magnetic pole
5 ... Spindle motor (SPM)
6 Head actuator
7. Voice coil motor (VCM)
8 Head amplifier circuit
80 ...... Light amplifier
81: Lead amplifier
9 Read / write circuit
90 …… Light channel
901: Recording compensation circuit
902 ... encoding circuit
91 ... Read channel
911: reproduction distortion compensation circuit
912: Waveform equalization circuit
10 HDC
11 ... Servo controller
12 CPU
13 ... FROM
14 ... RAM
15 ROM
16 ... lamp

Claims (12)

A magnetic recording medium,
A recording head that records information on the magnetic recording medium; and a magnetoresistive element that reproduces information from the magnetic recording medium and has a non-linear MR operation region with an external magnetic field below which causes failure of the recording head. A magnetic head comprising a reproducing head including
An external magnetic field detecting means for detecting an external magnetic field applied to the recording head by an external magnetic field distortion of the reproducing head including the magnetoresistive effect element,
External magnetic field obstacle avoidance means for avoiding an obstacle to the external magnetic field,
A magnetic disk drive comprising: a control unit that controls the external magnetic field detecting unit and the external magnetic field obstacle avoiding unit to avoid an obstacle caused by an external magnetic field. A read head including the magnetoresistive effect element, wherein the external magnetic field detecting unit has a non-linear area in an external magnetic field in which an operation area causes a failure of the recording head;
A reproduction distortion compensation circuit that compensates for reproduction distortion of the reproduction head;
A storage circuit for storing a reproduction distortion compensation amount without a magnetic field;
Compensation amount variation calculating means for calculating a compensation amount variation with respect to the initial compensation amount stored in advance in the storage circuit,
2. The magnetic disk drive according to claim 1, wherein the control unit acquires the compensation amount fluctuation calculated by the compensation amount fluctuation calculating unit as external magnetic field information. The external magnetic field disturbance avoiding means includes a storage circuit for storing a predetermined compensation amount variation, and prohibits a recording operation of the recording head when the compensation amount variation exceeds the predetermined value. The magnetic disk drive according to claim 2. The external magnetic field obstacle avoidance means, a storage circuit that stores a predetermined compensation amount fluctuation,
The magnetic head has a retreat area for retreat,
3. The magnetic disk drive according to claim 2, wherein when the compensation amount variation exceeds a predetermined value, the magnetic head retreats to the retraction area. The external magnetic field obstacle avoidance means, a recording compensation circuit that performs recording compensation,
A table storing a recording compensation amount corresponding to the compensation amount variation,
3. The magnetic disk drive according to claim 2, wherein recording compensation is performed based on the compensation amount fluctuation and information in the table. A read head including the magnetoresistive effect element, wherein the external magnetic field detecting unit has a non-linear area in an external magnetic field in which an operation area causes a failure of the recording head;
And a positioning accuracy detection circuit for detecting the positioning accuracy of the reproducing head,
2. The magnetic disk drive according to claim 1, wherein the positioning accuracy is obtained as external magnetic field information. The external magnetic field obstacle avoidance means, a storage circuit that stores a predetermined positioning accuracy,
7. The magnetic disk drive according to claim 6, wherein the recording operation of the recording head is prohibited when the positioning accuracy exceeds a predetermined value. The external magnetic field obstacle avoidance means, a storage circuit that stores a predetermined positioning accuracy,
The magnetic head has a retreat area for retreat,
7. The magnetic disk drive according to claim 6, wherein when the positioning accuracy exceeds a predetermined value, the magnetic head retreats to the retraction area. 9. The magnetic recording medium according to claim 8, wherein the retreat area is a track on the magnetic recording medium in which a radial distance between the reproducing head including the magnetoresistive element and the recording head is equal to or more than one track width. Disk device. 10. The magnetic disk drive according to claim 9, wherein the save area is an outermost track of the magnetic recording medium. 10. The magnetic disk drive according to claim 9, wherein external magnetic field detection is performed by the external magnetic field detection means in the evacuation area. A ramp member for retracting the magnetic head outside the magnetic recording medium,
10. The magnetic disk drive according to claim 9, wherein the retreat area is located on the ramp member.

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