JP2000251203A - Magnetic disk device and method for correcting characteristic of magnetoresistance effect type head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely correct characteristic deterioration of an MR head. SOLUTION: If a data error occurs in a read of data from a disk medium 11 by the MR head 12, a CPU 25 compares the resistance value of the MR head 12 measured by a resistance measuring circuit 191 in a head amplifier IC 19, with a reference resistance range which is stored in an FROM 26 and determined by the initial resistance value of the MR head 12 to detect whether the MR head 12 has been deteriorated in characteristics. Then when the deterioration in the characteristics is detected, the MR head 12 is moved back to a non-recording area 111 on a disk medium 11, or to a ramp 10 and a current generating circuit 192 supplies a refresh current to the MR head so as to correct the characteristics of the MR head 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive provided with a magnetoresistive head using a magnetoresistive element for reading data from a magnetic disk medium, and more particularly to characteristics of the magnetoresistive head. The present invention relates to a magnetic disk drive and a magnetoresistive head characteristic correction method suitable for correcting deterioration.

[0002]

2. Description of the Related Art In recent years, in a magnetic disk drive which records and reproduces data on a disk medium (magnetic disk medium) as a magnetic recording medium by using a magnetic head, one of means for realizing a high recording density is a high reproduction output. (Magneto Resistive) element (DSM), Dual Stripe Magneto Resistive (DSMR) element (double stripe magnetoresistive element), or GMR
(Giant Magneto Resistive) element (giant magnetoresistive element) was used as a data reading (data reproducing) element.
A so-called composite separation type magnetic head has been adopted. Here, these magnetic heads are collectively referred to as MR heads (magnetoresistive heads).

In this type of MR head, if the characteristics of the head deteriorate, there is a possibility that information recorded on a disk medium cannot be read correctly. Therefore, for example, in US Pat. No. 5,650,887, when the characteristic of the MR head deteriorates, the strength, direction and time of the current flowing through the MR head are appropriately selected and given to give the characteristic of the MR head. (Hereinafter, referred to as prior art) is described. Here, a current flowing through the MR head to correct the characteristics of the MR head is called a reset current.

In the above prior art, an automatic gain control (AGC) for keeping the amplitude of a head readout waveform (read signal waveform) constant is used to determine whether or not the characteristics of the MR head have deteriorated.
l) Judgment is made based on the gain amount (AGC gain amount) in the circuit. According to this determination method, when the characteristics of the MR head deteriorate, the amplitude of the head readout waveform decreases.
This is applied by paying attention to an increase in the C gain amount.

[0005]

There is a stage in the deterioration of the characteristics of the MR head, and the amplitude of the read waveform of the head gradually decreases until a certain state. Therefore, at this stage, it is possible to determine the characteristic deterioration of the MR head based on the AGC gain amount.

However, as the characteristics of the MR head deteriorate further, the magnetoresistive effect element of the head (ie, the MR head)
A phenomenon of magnetization reversal that does not return to the original state while the magnetization direction of the element (device) is changed occurs, and in this state, the amplitude is not always small but may be large. That is, as the characteristics of the MR head deteriorate, the AGC
With the determination method based on the gain amount, it is difficult to correctly determine the characteristic deterioration of the MR head.

Further, in the state where no magnetization reversal has occurred, it is possible to correctly determine the deterioration of the characteristics of the MR head based on the AGC gain amount. There is a possibility of inviting.

If a refresh current is applied while the MR head is positioned on the recording area of the disk medium, there is a possibility that data at the head position may be destroyed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a magnetic disk drive and a magnetoresistive head characteristic correction method capable of safely correcting the characteristic deterioration of a magnetoresistive head (MR head). Is to provide.

[0010]

According to the present invention, there is provided a magnetic disk apparatus provided with an MR head (magnetoresistive head) using a magnetoresistive element for reading data from a magnetic disk medium. A characteristic deterioration detecting means for detecting the presence or absence of characteristic deterioration, a current generating circuit for generating a current to be supplied to the MR head, and a control device having the following control means, that is, data read by the MR head. When an error occurs, the MR head is moved to a predetermined location other than the recording area on the magnetic disk medium or a predetermined location outside the magnetic disk medium in accordance with the detection of the presence of the characteristic degradation of the MR head by the characteristic degradation detecting means. Evacuation control means for retracting the MR head, and a state in which the MR head is retracted to the predetermined location by the control of the evacuation control means. In characterized by comprising a control device having a refresh current generation control means for generating and outputting a refresh current to the MR head by the current generating circuit in order to perform the characteristic correction of the MR head.

Here, the characteristic deterioration detecting means is connected to a resistance measuring circuit for measuring the resistance value of the MR head in which the data error (read data error) has occurred, or a read signal (head read waveform) read by the MR head. ), And a signal amplitude measuring circuit for measuring the amplitude of the signal based on the measurement result of the measuring circuit and a reference value (reference range).
It is preferable to use a determination means for determining the characteristic deterioration of the R head. Note that the signal amplitude measurement circuit uses the MR
Output waveform of a head amplifier circuit (head amplifier IC) for amplifying a read signal read by the head, or output of an AGC circuit in a read / write circuit (read / write IC) for amplifying the output of the head amplifier circuit to a certain level What is necessary is just to observe a waveform (however, a gain is fixed). If the reference value is set individually for each MR head in consideration of the variation in the characteristics of the MR head, the deterioration of the characteristics can be detected with high accuracy. This reference value may be determined based on an actual measurement at the stage of manufacturing the magnetic disk device, and may be stored in a nonvolatile memory in advance.

In such a configuration, when it is determined that the cause of the data error is deterioration of the characteristics of the MR head, when a refresh current is supplied to the MR head to correct the characteristics of the MR head, The head is retracted to a predetermined location other than the recording area on the magnetic disk medium or a predetermined location outside the magnetic disk medium, and thereafter the refresh current flows to the head. The possibility that the above data is destroyed can be eliminated. here,
In the case of a magnetic disk device to which the head load / unload method is applied, the predetermined portion (retreat portion) is a ramp (ramp mechanism) provided adjacent to the outer periphery of the disk medium and adjacent to the medium. In the case of a magnetic disk device to which the (contact start / stop) method is applied, a non-recording area called a CSS area secured in a predetermined area on a disk medium. It should be noted that this non-recording area may be secured in a magnetic disk device to which the load / unload method is applied.

Further, according to the present invention, when a reference signal in servo data previously recorded in a servo area arranged on a recording surface of a magnetic disk medium is read by an MR head, the polarity of the read reference signal is read. When a data error occurs during reading of data by the signal inversion identification circuit for identifying inversion / non-inversion and the following control means, that is, data reading by the MR head, the MR head reads the reference signal. Reference signal inversion discrimination control means for discriminating the polarity inversion / non-inversion of the reference signal by the signal inversion discrimination circuit; and when the signal reversal discrimination circuit identifies the polarity inversion of the reference signal read by the MR head. In addition, a current generation circuit generates and outputs a refresh current to the MR head in order to correct characteristics of the MR head. Also characterized in that a control device having a refresh current generation control means for.

In such a configuration, when a data error occurs in reading data by the MR head, the reference signal is read by the MR head, and the polarity inversion of the read reference signal can be confirmed. In this case, it is determined that the cause of the data error is deterioration of characteristics due to magnetization reversal of the MR head. By supplying a refresh current to the MR head in this magnetization reversal state, the refresh current is supplied in a state where no magnetization reversal occurs. Unlike the case of flowing, the possibility that the MR head is destroyed can be eliminated.

Before generating and outputting a refresh current to the MR head in the magnetization reversal state,
If a retreat control means for retreating the head to the predetermined position is provided in the control device, it is possible to eliminate the possibility that data in the recording area of the disk medium is destroyed by flowing the refresh current.

Further, according to the present invention, when it is determined that the cause of the data error is deterioration of the characteristics of the MR head,
Whether the characteristic deterioration has progressed to the magnetization reversal state,
The reference signal in the servo data is read by the MR head, and the read reference signal is checked for polarity reversal to determine whether or not the polarity of the read reference signal is reversed. For that MR
A refresh current is supplied to the head. Further, according to the present invention, even when it is not possible to judge from the detection result of the characteristic deterioration detecting means that the data error has occurred due to the characteristic deterioration of the MR head, the reference signal is read by the MR head and the read reference value is read. If the polarity reversal of the signal can be identified, it is determined that the characteristic deterioration of the MR head has progressed to the magnetization reversal state.
It is also characterized in that a refresh current is supplied to the MR head for correcting the characteristics of the R head.

That is, according to the present invention, when a data error occurs, the reference signal is read by a corresponding MR head, and when the polarity inversion of the read reference signal can be identified, the detection result of the characteristic deterioration detecting means is obtained. Irrespective of the above, a refresh current is caused to flow through the MR head to correct the characteristics of the MR head.

As described above, the MR in which a data error has occurred
By reading the reference signal by the head and identifying the polarity inversion of the read reference signal, the magnetization reversal state of the MR head, that is, M
It is possible to determine the state in which the characteristic deterioration of the R head has progressed. In addition, by supplying a refresh current to the MR head in this state, the characteristics of the MR head can be safely corrected.

Further, according to the present invention, the M
When the characteristic deterioration of the R head is detected by the characteristic deterioration detecting means, and when the non-inversion of the polarity of the reference signal read by the MR head is identified, a refresh current for further deteriorating the characteristics of the MR head. The characteristic deterioration current in the opposite direction to that of the MR
It is also characterized in that the head is made to generate and output.

As described above, for the MR head in which the characteristic deterioration is detected by the characteristic deterioration detecting means but is not in the magnetization reversal state, a characteristic deterioration current is supplied to the MR head to force the MR head into the magnetization reversal state. By confirming the magnetization reversal state and then passing a refresh current through the MR head, the characteristics of the MR head can be corrected safely.

Here, if the control device is provided with a retreat control means for retreating the MR head to the predetermined location before generating and outputting the refresh current or the characteristic deterioration current to the MR head in the magnetization reversal state, It is possible to eliminate the possibility that data in the recording area of the disk medium is destroyed by flowing the refresh current or the characteristic deterioration current.

Note that even if a refresh current is applied, the polarity inversion of the reference signal read by the corresponding MR head is not eliminated, that is, if the magnetization inversion state is not eliminated, or even if a characteristic deterioration current is applied, the reference signal is output. If the polarity does not reverse, that is, if the magnetization is not reversed, the current application conditions (refresh current or characteristic degradation current generation / output conditions) are stepwise adjusted in the direction in which stronger current is applied until the desired state is achieved. (At least one of the current value and the current application time is increased).

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the loading / loading of a head.
An embodiment implemented in a magnetic disk device to which the unload method is applied will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a magnetic disk drive according to one embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a disk medium (magnetic disk) on which data is recorded. A large number of concentric tracks (not shown) are formed in a recording area (data zone) 112 on each surface (recording surface) of the disk medium 11, and each track has a servo used for seeking and positioning of a head. Servo areas 113 on which data is recorded are arranged at equal intervals. A user area 114 is provided between the servo areas 113, and a plurality of sectors (data sectors) as recording units are arranged in the user area 114. The servo areas 113 are radially arranged on the disk medium 11 over the tracks from the center at equal intervals.

The servo area 113 has an AGC in which data of a constant frequency is recorded in order to stabilize the signal amplitude.
A reference signal area in which a reference signal of a specific signal pattern as shown in FIG. 7 is used for identifying (detecting) an area and a servo area and determining a reference position, a cylinder address (cylinder code) indicating a cylinder number, and the cylinder concerned It is composed of an address / burst area in which burst data for indicating a position error in a cylinder indicated by an address by a waveform amplitude is recorded. Above servo area 113
Is omitted in the figure because it is well known in the art.

For example, the innermost peripheral area of the disk medium 11 is
A non-recording area (non-data zone) 111 in which data is not recorded so that the MR head 12 can be retracted. In the configuration of FIG. 1, a single disk medium 11
Are assumed, but a configuration in which a plurality of disk media are stacked and arranged may be used.

On each surface (recording surface) side of the disk medium 11, a magnetoresistive element (MR element) is used to read data (reproduce data) from the disk medium 11 and write data to the disk medium 11. (Data recording)
Heads (magnetoresistive heads) 12, each of which is formed using a thin-film element, are provided.

The MR head 12 is attached to the tip of an arm 13a of a rotary head actuator 13 as a head moving mechanism, and moves in the radial direction of the disk medium 11 according to the rotation (angular rotation) of the head actuator 13. Thus, the MR head 12 seeks and positions on the target track. A ramp (ramp mechanism) 1 outside the outer periphery of the disk medium 11 for retracting the MR head 12 when the rotation of the disk medium 11 is stopped or the like.
0 is arranged. The ramp 10 is provided at a predetermined position on the movement path of the tip (tab) of the arm 13a of the head actuator 13 in the vicinity of the disk medium 11.

The disk medium 11 is rotated at a high speed by a spindle motor (hereinafter referred to as SPM) 14. The head actuator 13 is the head actuator 1
3 has a voice coil motor (hereinafter, referred to as VCM) 15 serving as a driving source, and is driven by the VCM 15.

The SPM 14 is driven by an operation current (SPM current) supplied from the SPM driver 16. V
The CM 15 (the head actuator 13 having the CM 15)
It is driven by an operation current (VCM current) supplied from the CM driver 17. In the present embodiment, the SPM driver 16 and the VCM driver 17 are realized by a motor driver IC 18 integrated on one chip. VCM is sent from SPM driver 16 to SPM 14.
The value (operation amount) for determining the operation current supplied from the driver 17 to the VCM 15 is determined by the CPU 25.

After seeking and positioning on the target track, the MR head 12 scans the track by rotating the disk medium 11. MR head 12
Scans the servo data of the servo areas arranged at equal intervals on the track by scanning. The MR head 12 reads and writes data from and to a target data sector by scanning.

The MR head 12 is connected to a head amplifier IC (head amplifier circuit) 19 mounted on a flexible printed circuit (FPC). Head amplifier IC
19 is the MR head 1 (according to the control from the CPU 25)
2 and the input / output of read / write signals to / from the MR head 12. The head amplifier IC 19 is an MR
The read signal (from the MR head 12) read by the head 12 is amplified, and the write data sent from the read / write IC (read / write circuit) 20 is subjected to predetermined signal processing, and the read data is sent to the MR head 12. send.

The head amplifier IC 19 is provided for the MR head 12
Resistance measurement circuit 19 for measuring the resistance value of (MR element)
1. The MR head 12 (of the MR head 12)
And a current generating circuit 192 for generating a current flowing through the element. The current generated by the current generation circuit 19 includes a bias current used during normal reading, a refresh current used to correct the characteristic deterioration of the MR head 12, and the MR head 12 according to the mode (purpose of use).
Are forcibly set to the magnetization reversal state.

FIG. 2 shows a waveform example of the refresh current.
The refresh current has a direction opposite to the bias current flowing at the time of reading, for example, current values I11 and I12 (| I11 |
> | I12 |), and flows for times T11 and T12, respectively.
Next, a waveform example of the characteristic deterioration current is shown in FIG. This characteristic degradation current is in the same direction as the bias current that flows during reading,
For example, the current flows between times T21 and T22 at current values I21 and I22 (| I21 |> | I22 |), respectively. The current value of the above current,
The direction (polarity) and time can be arbitrarily set by the CPU 25.

The read / write IC 20 is an MR head 1
AGC (automatic gain control) for amplifying a read signal (head amplifier output waveform) read from the disk medium 11 by the head amplifier 2 and amplified by the head amplifier IC 19 to a constant amplitude.
And a decoding function (read channel) for performing signal processing necessary for decoding the read signal amplified by the AGC function into, for example, NRZ code data, and a signal processing required for recording data on the disk medium 11. An encoding function (write channel) to be performed; a pulse function for pulsing the read signal to output servo data from the read signal to output as pulsed read data; A function of extracting burst data in the servo data according to a timing signal (burst timing signal). This burst data is sent to the CPU 25, and M
It is used for positioning control for positioning the R head 12 at a target position on a target track.

The read / write IC 20 includes an AGC circuit 201 for realizing the AGC function, a signal amplitude measuring circuit 202 for measuring the amplitude of an output signal of the AGC circuit 201, and a reference signal in the output signal of the AGC circuit 201. A signal inversion identification circuit 203 for identifying the polarity inversion (positive / negative inversion) of the pattern is incorporated. The timing of this reference signal is indicated by a reference signal reading timing signal from the gate array 21.

The gate array 21 is a read / write IC
20 from the read pulse output from servo area 1
13 has a reference signal detection function of detecting (extracting) a reference signal of a specific signal pattern included in the servo data recorded in the servo data. Here, the gate array 21 includes a signal pattern (specific signal pattern) specific to the reference signal and a signal pattern specific to the reference signal so that the reference signal can be detected even when the polarity of the signal pattern of the reference signal is inverted due to deterioration of the characteristics of the MR head 12. A pulse train of two kinds of reference patterns corresponding to each of the signal patterns whose polarity is inverted (elevation suppression inverted specific signal pattern) is provided, and a read pulse train that matches one of the pulse trains of the two kinds of reference patterns is provided. By detecting, the reference signal is detected.

In response to the detection of the reference signal, the gate array 21 determines the timing of the servo signal indicating the timing of the next servo area 113 and the timing of the reference signal of the next servo area 113 (in the servo data recorded in the servo area 113). It has a function of generating various timing signals including a reference signal read timing signal representing the timing of the burst data and a burst timing signal representing the timing of the burst data, and a function of extracting a cylinder address in the servo data. This cylinder address is sent to the CPU 25 and used for seek control for moving the MR head 12 to a target track.

The buffer memory 22 is data (write data) to be transferred from the host (host system) and written to the disk medium 11 and data to be read from the disk medium 11 and transferred to the host (read data).
Is used to temporarily store The buffer memory 22 is a rewritable memory such as a RAM (Random Ac
cess Memory).

The disk controller (HDC) 23
It manages commands (write command, read command, etc.) with the host, data communication, buffer control, data transfer control with the disk medium 11 and the like. The disk controller 23 incorporates an error detection circuit (not shown) for detecting an error (read data error) in the read data decoded by the read / write IC 20.

The CPU 25 has a flash memory R as a rewritable nonvolatile memory in which a control program is stored.
An OM (Read Only Memory) 26, a RAM 27 that provides a work area for the CPU 25, and a D / A (digital / analog) converter (hereinafter, referred to as DAC) 28
Built-in. A flash ROM (hereinafter referred to as FROM) 26 stores, in addition to the control program, a resistance value (initial resistance) of each MR head 12 (an MR element thereof) measured in an inspection at the time of manufacturing the magnetic disk device of FIG. ), And a reference amplitude value in the case where the AGC gain amount is fixed, which is determined from the amplitude value of the output signal waveform of the AGC circuit 201, is stored in advance for each MR head 12.

The CPU 25 controls the entire device (HDD) in accordance with the control program stored in the FROM 26, for example, the MR head 12 based on the cylinder code extracted by the gate array 21 and the burst data extracted by the read / write IC 20. H according to seek / positioning control, read / write command from host
The read / write control by the DC 23 is executed.

When the disk controller 23 detects a read data error, the CPU 25
The presence or absence of the characteristic deterioration of the R head 12 is checked, and when the characteristic deterioration is determined, the generation of the current to the MR head 12 by the current generating circuit 192 in the head amplifier IC 19 is controlled to correct the characteristic deterioration. This control is realized by setting three parameters of the current value (absolute value), current direction (polarity), and time (current supply time) in the current generation circuit 192.

Next, for example, four types of read data error processing (first to fourth read data error processing) including MR head characteristic deterioration correction processing applicable to the magnetic disk device having the configuration shown in FIG. explain.

(1) First Read Data Error Processing First, the first read data error processing will be described with reference to the flowchart of FIG. The first read data error processing is characterized in that the characteristic deterioration of the MR head 12 is determined based on the resistance value of (the MR element of) the MR head 12 and the refresh current is applied to the MR head 12. The point is that the operation is performed in a state where the MR head 12 is positioned (retracted) on the non-recording area 110 of the disk medium 11 or the ramp 10.

Now, it is assumed that a read command has been issued from the host to the magnetic disk device having the configuration shown in FIG.
This read command is received by the disk controller 23. Upon receiving the command from the host, the disk controller 23 issues an interrupt to that effect to the CPU 25.
Emit to The CPU 25 receives and interprets the received command (here, the read command) from the disk controller 23 by this interrupt.

The CPU 25 includes a disk controller 23
If the command received from the disk controller 23 is a read command, in order to perform a disk read operation in the range requested by the command, information on the physical position on the disk of the first sector of the range to be accessed and the number of sectors to be accessed are stored in the disk controller 23. A register (not shown) provided therein is set, and the head amplifier IC 19 selects the MR head 12 corresponding to the disk surface to be accessed.

Subsequently, the CPU 25 sends the VCM driver 17
To control the VCM 15 to move the MR head 12 to the track where the sector to be accessed exists (seek).

The servo data recorded in the servo area on the disk medium 11 and the data recorded in each data sector in the user area are read by the MR head 12, and the read signal is amplified by the head amplifier IC 19. . The read signal amplified by the head amplifier IC 19 is input to the read / write IC 20.

AGC circuit 2 in read / write IC 20
01 is a read signal amplified by the head amplifier IC 19, the gain of which is adjusted by the AGC function so that the amplitude of the output waveform of the signal recorded in the AGC area becomes constant. Stabilize the amplitude of The read / write IC 20 binarizes a read signal whose amplitude is stabilized by the AGC circuit 201 by a binarization function, converts the binarized signal into a pulse train (read pulse), and outputs it to the gate array 21.

The gate array 21 is a read / write IC
A reference signal in the servo data recorded in the servo area 113 is detected based on the read pulse output from the reference signal 20, and a start bit indicating the detection timing is generated. A servo gate signal indicating the timing of the servo area 113, a reference signal reading timing signal corresponding to a reference signal of (in the servo data recorded in) the next servo area 113,
A timing signal (burst timing signal) corresponding to the burst data, a timing signal (address timing signal) corresponding to the cylinder address, and the like are generated. The reference signal read timing signal and the burst timing signal are output to the read / write IC 20.

The read / write IC 20 is an AGC circuit 2
The burst data is extracted from the read signal whose amplitude has been stabilized by 01 in accordance with the burst timing signal output from the gate array 21. This burst data is converted into digital data by an A / D converter (not shown) and sent to the CPU 25.

On the other hand, the gate array 21 extracts the cylinder address in the servo data from the read pulse and sends it to the CPU 25 at a timing according to the address timing signal generated by the gate array 21 itself. Gate array 21
Generates a data sector pulse indicating the timing of each data sector position arranged in the user area according to the servo gate generated by itself,
Output to 3.

Every time the gate array 21 extracts a cylinder address (of the cylinder where the MR head 12 is currently located), the CPU 25 compares the cylinder address with the cylinder address of the target cylinder. The amount of operation required to seek (move) the MR head 12 to the target cylinder is calculated. And CPU
Numeral 12 performs seek control for seeking the MR head 12 to the target cylinder by giving the operation amount to the VCM driver 17 and driving the VCM 15 by the VCM driver 17.

When the CPU 25 causes the MR head 12 to perform a target cylinder seek, every time burst data is extracted by the read / write IC 20, the MR 25 is set on the basis of the burst data (the digital conversion value of the A / D converter with respect to the burst data). A position error of the head 12 in a target cylinder from a target position is calculated, and the VCM 15 is driven and controlled through the VCM driver 17 based on the position error, thereby performing positioning control for positioning the MR head 12 at the target position.

The disk controller 23 has a CPU 25
When the MR head 12 reaches the position of the start data sector of the access target while the MR head 12 is positioned at the target position of the target cylinder by the seek / positioning control described above, a read circuit, a so-called read gate, is opened. As a result, the data on the disk medium 11 is sequentially read from the target sector and transferred to the disk controller 23 via the head amplifier IC 19 and the read / write IC 20. For example, the presence or absence of an uncorrectable read data error is checked. You.

If the occurrence of a read data error is detected, the CPU 25 starts the read data error processing according to the flowchart of FIG.
The resistance value of the currently selected MR head 12, that is, the MR head 12 in which a read data error has occurred is measured by the resistance measurement circuit 191 in C19 (step S).
1) Compare the measurement result (resistance value) with the reference resistance range determined based on the resistance value (initial resistance value) of the MR head 12 at the time of manufacturing the magnetic disk device and stored in the FROM 26 ( Step S2). In addition, FRO
The initial resistance value of each MR head 12 at the time of manufacturing the magnetic disk device may be stored in M26, and the reference resistance range may be sequentially calculated based on the initial resistance value.

As a result of the comparison, when the resistance value of the MR head 12 in which the read data error has occurred is out of the reference resistance range, the CPU 25 determines that the cause of the read data error is due to the characteristic deterioration of the MR head 12. judge. In this case, the CPU 25 drives the VCM 15 via the VCM driver 17 so that the MR head 12
Alternatively, it temporarily retreats to the non-recording area 111 on the disk medium 11 (step S3).

Then, the CPU 25 sends an instruction to the current generating circuit 192 in the head amplifier IC 19 in order to correct the characteristic deterioration of the MR head 12, and corresponds to the resistance value of the MR head 12 as shown in FIG. Then, a refresh current having the waveform of (1) is generated and output to the MR head 12 (step S4). At this time, since the MR head 12 is retracted on the ramp 10 or the non-recording area 111 of the disk medium 11, the refresh current is supplied to the MR head 1
2, the recording area 1 on the disk medium 11
There is no risk that the 12 recorded data will be destroyed.

Next, the CPU 25 measures the resistance value of the MR head 12 to confirm that the characteristic deterioration of the MR head 12 (in which a read data error has occurred) has been corrected normally by the application of the refresh current. 191
Is measured again, and compared with the reference resistance range (steps S5 and S6).

If the resistance value of the MR head 12 is still outside the reference resistance range, the CPU 25 determines that the characteristic deterioration of the MR head 12 has not been corrected normally even when the refresh current is applied. In this case, C
The PU 25 changes the application condition of the refresh current to the current generation circuit 192 in the direction in which the stronger refresh current is applied, that is, increases the current value I11 or I12 or the time T11 or T12 in FIG. (Step S7), the process returns to step S4, and the corresponding refresh current is generated by the current generating circuit 192 and output to the MR head 12.

The CPU 25 repeats the above operation until the resistance value of the MR head 12 falls within the reference resistance range (step S6). When the resistance value of the MR head 12 falls within the reference resistance range, the CPU 25
Assuming that the characteristic deterioration of the head 12 has been corrected, the MR head 12 seeks and positions at the target position of the target cylinder and performs normal error recovery (read retry) (step S8). An upper limit may be set for the number of repetitions, and when the number of times exceeds the upper limit, a warning may be notified to the user via a user interface or the like of the host.

On the other hand, if the resistance value measured first is within the reference resistance range (step S2), the CPU
In step S8, it is determined that there is no read data error due to deterioration of the characteristics of the MR head 12, and normal error recovery (read retry) is performed as it is (step S8).

(2) Second Read Data Error Processing Next, the second read data error processing will be described with reference to the flowchart of FIG. The feature of the second read data error processing is that the characteristic deterioration of the MR head 12 is based on the amplitude of the read signal (head readout waveform) from the MR head 12, and more specifically, (from the head amplifier IC 19. Corresponding to the output signal amplitude)
AGC circuit 20 with AGC gain fixed
1 based on the amplitude of the output signal from
The application of the refresh current to the R head 12
This is performed in a state where the head 12 is retracted on the non-recording area 111 of the disk medium 11 or the lamp 10.

Now, it is assumed that a read data error has occurred in the magnetic disk drive of FIG. In this case, the CPU 25
Starts the read data error processing according to the flowchart of FIG.
That is, the read signal (head read waveform) read by the MR head 12 in which the read data error has occurred and amplified by the head amplifier IC 19 is obtained by fixing the AGC gain of the AGC circuit 201 in the read / write IC 20 to a predetermined value. In this state, the signal is amplified by the AGC circuit 201, and the amplitude of the output signal of the AGC circuit 201 is measured by the signal amplitude measurement circuit 202 in the read / write IC 20 (step S11). And the CPU 25
The FROM corresponding to the measured signal amplitude (measured signal amplitude) and the MR head 12 in which the read data error has occurred.
26 is compared with the reference amplitude value stored in step S26 (step S12).

As a result of the above comparison, if the signal amplitude measurement value (the amplitude of the output signal of the AGC circuit 201 corresponding to the read signal from the MR head 12 in which the read data error has occurred) is smaller than the reference amplitude value, the CPU 25 reads the read data. It is determined that the cause of the error is due to the characteristic deterioration of the MR head 12.

In this case, the CPU 25 moves the MR head 12 to the lamp 10 or the non-recording area 1 on the disk medium 11.
11 (step S13), and a head amplifier IC for correcting the characteristic deterioration of the MR head 12.
An instruction is sent to the current generating circuit 192 in the CPU 19 to generate a refresh current having the waveform of FIG. 2 corresponding to the signal amplitude measurement value and output the refresh current to the MR head 12 (step S14). At this time, the MR head 12 is
0 or has been saved on the non-recording area 111 of the disk medium 11, so that the refresh current is
The recording area 11 on the disk medium 11
There is no possibility that the recording data of No. 2 will be destroyed.

Next, the CPU 25 changes the amplitude of the output signal of the AGC circuit 201 to the signal amplitude in order to confirm that the characteristic deterioration of the MR head 12 (in which a read data error has occurred) has been corrected normally by the application of the refresh current. The measurement is performed again by the measurement circuit 202 and compared with the reference amplitude value (steps S15 and S16).

If the signal amplitude measurement value is still smaller than the reference amplitude value, the CPU 25 determines that the characteristic deterioration of the MR head 12 has not been corrected normally and sends a signal to the current generation circuit 192 of FIG. Current value I11 or I1
2, or instruct the increase of the time T11 or T12 (step S17), return to the step S14, and generate the corresponding refresh current by the current generating circuit 192;
The output is made to the MR head 12.

The CPU 25 repeats the above operation until the measured signal amplitude value becomes equal to or larger than the reference amplitude value (step S1).
6) Execute repeatedly. When the measured signal amplitude value is equal to or greater than the reference amplitude value, the CPU 25 sets the MR head 1
2 that the characteristic deterioration of the MR head 12 has been corrected.
To the target position of the target cylinder to perform normal error recovery (read retry) (step S18). An upper limit may be set for the number of repetitions, and when the number of times exceeds the upper limit, a warning may be notified to the user via a user interface or the like of the host.

On the other hand, when the first signal amplitude measurement value is equal to or larger than the reference amplitude value (step S12), C
The PU 25 determines that there is no read data error due to deterioration of the characteristics of the MR head 12, and performs normal error recovery (read retry) as it is (step S18).

In the second read data error processing described above, the amplitude of the read signal from the MR head 12 used for determining the characteristic deterioration of the MR head 12 is represented by AG.
The case where the amplitude of the output signal from the AGC circuit 201 is measured in a state where the C gain amount is fixed has been described, but the amplitude of the input signal of the AGC circuit 201, that is, the amplitude of the output signal from the head amplifier IC 19 is measured. It does not matter. In this case, it is not necessary to fix the AGC gain amount of the AGC circuit 201.

(3) Third Read Data Error Process Next, the third read data error process will be described with reference to the flowchart of FIG. The feature of the third read data error processing is that the characteristic deterioration of the MR head 12 is determined by the presence / absence of signal inversion (polarity inversion) of the reference signal read by (the MR element of) the MR head 12. The application of the refresh current to the MR head 12 is performed in a state where the MR head 12 is retracted on the non-recording area 111 of the disk medium 11 or on the ramp 10.

Assume that a read data error has occurred in the magnetic disk drive of FIG. In this case, the CPU 25
Starts the read data error processing according to the flowchart of FIG.
The reference signal in the servo data recorded in advance is read by the currently selected MR head 12, that is, the MR head 12 in which a read data error has occurred, and the presence / absence of the polarity inversion of the signal pattern is read / written. IC
Control is performed for identification by the signal inversion identification circuit 203 in step 20 (step S21). Then, the signal inversion discrimination circuit 203 is read by the MR head 12 in which the read data error has occurred, and is read by the head amplifier IC 19,
Further, of the read signals amplified by the AGC circuit 201 in the read / write IC 20, the gate array 21
, The presence / absence of the polarity reversal of the signal pattern is identified for a read signal that matches the timing indicated by the reference signal read timing signal from the controller, ie, the reference signal in the servo data.

Now, assuming that the waveform of the reference signal is as shown in FIG. 7, when the characteristics of the MR head 12 are normal, the read signal obtained when the reference signal is read by the MR head 12 is used. Waveform, for example, head amplifier IC 19
8A is as shown in FIG. 8A, and the polarity of the signal pattern does not reverse. On the other hand, when the characteristics of the MR head 12 are degraded due to the magnetization reversal, the waveform of the read signal (the waveform of the output signal of the head amplifier IC 19) when the reference signal is read by the MR head 12 is shown in FIG.
As shown in (b), the polarity of the signal pattern is inverted.

The CPU 25 determines whether or not the polarity (positive / negative) of the signal pattern is inverted based on the result of the identification by the signal inversion identifying circuit 203 (step S22). If the signal pattern is inverted as shown in FIG. It is determined that the cause of the read data error is due to the magnetization reversal of the MR element of the MR head 12 (characteristic degradation).

In this case, the CPU 25 moves the MR head 12 to the lamp 10 or the non-recording area 1 on the disk medium 11.
11 (step S23), and a head amplifier IC for correcting the characteristic deterioration of the MR head 12.
An instruction is sent to the current generation circuit 192 in FIG.
A refresh current having the waveform shown in FIG. 4 is generated and output to the MR head 12 (step S24). At this time, M
Since the R head 12 is in the magnetization reversal state, there is no possibility that the MR head 12 is destroyed by flowing the refresh current to the MR head 12. Further, the MR head 12 is mounted on the lamp 10 or the non-recording area 111 of the disk medium 11.
Since it is retracted upward, there is no danger that the recording data in the recording area 112 on the disk medium 11 will be destroyed by flowing the refresh current through the MR head 12.

Next, in order to confirm that the characteristic deterioration of the MR head 12 (in which a read data error has occurred) has been corrected normally by applying the refresh current, the servo of the disk medium 11 is again performed by the MR head 12. A reference signal is read from the area 113, and control is performed for the reference signal to determine whether or not the polarity is inverted by the signal inversion identification circuit 203 in the read / write IC 20, and the identification result in the signal inversion identification circuit 203 is performed. Then, it is determined whether the polarity of the signal pattern is inverted (steps S25 and S26).

If the polarity of the signal pattern is still inverted, the CPU 25 determines that the characteristic deterioration of the MR head 12 has not been corrected normally, and sends the current value I11 of FIG. Or, I12 or an instruction to increase the time T11 or T12 (Step S
27). Then, the CPU 25 returns to the step S23, temporarily evacuates the MR head 12 to the non-recording area 111 on the lamp 10 or the disk medium 11, and then corrects the characteristic deterioration of the MR head 12 by using the head amplifier IC1.
9, a refresh current is generated under the conditions specified in step S27 and output to the MR head 12 (step S24).

The CPU 25 repeats the above operation until the polarity of the signal pattern of the reference signal read by the MR head 12 does not reverse (step S26).

When the polarity of the signal pattern of the reference signal read by the MR head 12 does not reverse,
Assuming that the characteristic deterioration of the MR head 12 has been corrected, the CPU 25 seeks and positions the MR head 12 at the target position of the target cylinder and performs normal error recovery (read retry) (step S28). An upper limit may be set for the number of repetitions, and when the number of times exceeds the upper limit, a warning may be notified to the user via a user interface or the like of the host.

Here, when generating and outputting the first refresh current, the resistance value of the MR head 12 or M
The amplitude of the read signal from the R head 12 (head amplifier I
If the amplitude of the output waveform of C19 or the amplitude of the output waveform of the AGC circuit 201 when the AGC gain is fixed is measured, the first refresh current application condition can be appropriately set from the measured value.

On the other hand, if the inversion of the signal pattern is not determined in the first reading of the reference signal (step S22), the CPU 25 determines that there is no read data error due to the magnetization reversal of the MR head 12, and the normal operation is continued. Error recovery (read retry) is performed (step S28).

(4) Fourth Read Data Error Processing Next, the fourth read data error processing will be described with reference to the flowcharts of FIGS. The feature of the fourth read data error processing is that the second and third read data error processing are combined, and the signal amplitude measurement value (the MR head 1 in which the read data error occurs) is combined.
2 is greater than or equal to the reference amplitude value, the corresponding MR signal is output.
After confirming that the head 12 is in the magnetization reversal state,
Alternatively, the point is that a refresh current is caused to flow through the MR head 12 after forcibly reversing the magnetization of the MR head 12.

Now, it is assumed that a read data error has occurred in the magnetic disk drive of FIG. In this case, the CPU 25
Starts the read data error processing according to the flowcharts of FIGS. 9 and 10, and is first read out by the currently selected MR head 12, that is, the MR head 12 in which the read data error has occurred, and amplified by the head amplifier IC19. The read signal (head read waveform) is amplified by the AGC circuit 201 with the AGC gain of the AGC circuit 201 in the read / write IC 20 fixed, and the amplitude of the output signal of the AGC circuit 201 is read / written. The measurement is performed by the signal amplitude measurement circuit 202 in the IC 20 (step S31). And CPU25
Are FR corresponding to the measured signal amplitude (measured signal amplitude) and the MR head 12 in which the read data error has occurred.
A comparison is made with the reference amplitude value stored in the OM 26 (step S32).

As a result of the above comparison, even when the measured signal amplitude is equal to or larger than the reference amplitude, the CPU 25 determines whether or not the characteristics of the MR head 12 may be degraded due to the magnetization reversal. If the determination is successful, step S21 in the third read data error processing for correcting the characteristic deterioration of the MR head 12 by flowing a refresh current to the MR head 12 is performed.
To S28 (steps S41 to S4
Perform 8).

On the other hand, if the result of the comparison in step S32 shows that the measured signal amplitude is smaller than the reference amplitude, the CPU 25 determines that the cause of the read data error is the characteristic deterioration of the MR head 12 to which the read data error corresponds. And M
A series of processes that can correct the characteristic degradation without causing the destruction of the R head 12 are performed as follows.

First, the CPU 25 causes the MR head 12 in which a read data error has occurred to read a reference signal from the servo area 113 of the disk medium 11, and targets the reference signal to a signal inversion identification circuit 203 in the read / write IC 20. Is performed to determine the presence or absence of the polarity inversion, and the presence or absence of the polarity inversion of the signal pattern is determined from the identification result of the signal inversion identification circuit 203 (step S5).
1, S52).

If the polarity of the signal pattern is inverted, the CPU 25 proceeds to the corresponding MR head 12 in this state.
It is assumed that there is no danger that the MR head 12 will be destroyed even if a refresh current is supplied to step S43.
The following processing is performed, and the deterioration of the characteristics of the MR head 12 is corrected by applying a refresh current to the MR head 12 in a state where the MR head 12 is retracted onto the non-recording area 111 of the lamp 10 or the disk medium 11. I do.

On the other hand, if the polarity of the signal pattern is not inverted, the CPU 25 proceeds to the corresponding MR head 1 in this state.
It is determined that when a refresh current is supplied to the MR head 2, the MR head 12 may be broken. In this case, CPU2
5 forcibly reverses the magnetization of the corresponding MR head 12 as follows.

First, the CPU 25 retracts the MR head 12 onto the lamp 10 or the recording area 111 of the disk medium 11 (step S53). In this state, the CPU 25
Sends an instruction to the current generating circuit 192 in the head amplifier IC 19 to forcibly reverse the magnetization of the MR head 12 to generate a characteristic deterioration current having the waveform shown in FIG. (Step S54).

Next, the CPU 25 applies the characteristic deterioration current to the MR head 12 (where a read data error has occurred).
In order to confirm whether or not the deterioration of the characteristics of the MR head 12 has caused the magnetization reversal state of the MR head 12, the reference signal is again read from the servo area 113 of the disk medium 11 by the MR head 12, and the reference signal is And lead /
The signal inversion discrimination circuit 203 in the write IC 20 performs control for discriminating the presence / absence of polarity inversion, and from the result of identification by the signal inversion discrimination circuit 203, determines whether or not the signal pattern has polarity inversion (steps S55 and S56).

If the polarity of the signal pattern is not yet inverted, the CPU 25 determines that the MR head 12 is not in the magnetization inversion state, and the current generation circuit 1
92, the current value I21 or I22 in FIG. 3 or the time T21 or T22 is increased (step S5).
7). Then, the CPU 25 returns to step S53 and returns to M
After the R head 12 is temporarily retracted to the ramp 10 or the non-recording area 111 on the disk medium 11, the MR head 1
In order to reverse the magnetization of No. 2, the current generation circuit 192 in the head amplifier IC 19 generates a characteristic deterioration current under the conditions specified in step S57 and outputs the current to the MR head 12 (step S54).

The CPU 25 repeats the above operation until the polarity of the signal pattern of the reference signal read by the MR head 12 becomes inverted, that is, until the magnetization of the MR head 12 is inverted (step S56). Execute.

When the polarity of the signal pattern of the reference signal read by the MR head 12 is reversed, the CPU 25 determines that the MR head 12 is in the magnetization reversal state, and in this state, the MR head 12 is in the reverse state. Assuming that there is no danger of causing the destruction of the MR head 12 even if a refresh current is supplied to the head 12, the processing after step S43 is performed as it is, and the MR head 12 is placed on the ramp 10 or the non-recording area 111 of the disk medium 11. By flowing a refresh current through the MR head 12 in the retracted state, the characteristic deterioration of the MR head 12 is corrected.

An upper limit is set for the number of repetitions described above.
When the number of times exceeds the upper limit, a warning may be notified to the user via a user interface or the like of the host.

In the above, the case where the present invention is applied to a magnetic disk device to which the load / unload method of the head is applied has been described. The present invention can be similarly implemented as long as the magnetic disk device has a non-recording area 111 where the head 12 can be retracted. Normally, in a magnetic disk drive to which the load / unload method is not applied, the M
Since a CSS (contact start / stop) area (called a non-recording area) in which the R head 12 is retracted is secured, this CSS area can be used as the non-recording area 111.

[0098]

As described in detail above, according to the present invention, M
When the deterioration of the characteristics of the R head is determined, a refresh current is supplied to the MR head in a state where the MR head is retracted to a predetermined location other than the recording area on the disk medium or to a predetermined location outside the disk medium. By compensating the characteristic deterioration of the above, it is possible to eliminate the possibility that the data recorded in the recording area of the disk medium is destroyed due to the application of the refresh current.

Further, according to the present invention, in a state where the magnetization reversal of the MR head is confirmed, a refresh current is supplied to the MR head to correct the deterioration of the characteristics of the MR head. The possibility of being destroyed can be eliminated.

According to the present invention, when the characteristic deterioration of the MR head is determined and the magnetization reversal of the MR head is not performed, the characteristic deterioration current having a direction opposite to the refresh current is supplied to the MR head. Then, the MR head is forcibly inverted, and after confirming the magnetization inversion, a refresh current is applied to the MR head to correct the characteristic deterioration of the MR head, so that the head is destroyed by the application of the refresh current. Can be eliminated.

Further, according to the present invention, even when the characteristic deterioration of the MR head cannot be determined based on the amplitude of the read waveform from the MR head or the resistance value of the MR head, the magnetization reversal of the MR head can be confirmed. By properly determining the deterioration of the characteristics of the MR head and supplying a refresh current to the MR head in this state, the deterioration of the characteristics of the head is corrected while preventing the head from being damaged by the application of the refresh current. be able to.

As described above, according to the present invention, it is possible to safely correct the characteristic deterioration of the MR head.

[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 an exemplary view showing a waveform example of a refresh current applied in the embodiment.

FIG. 3 is an exemplary view showing a waveform example of a characteristic deterioration current applied in the embodiment.

FIG. 4 is an exemplary flowchart for explaining first read data error processing applicable to the embodiment;

FIG. 5 is an exemplary flowchart for explaining a second read data error process applicable to the embodiment;

FIG. 6 is an exemplary flowchart for explaining a third read data error process applicable in the embodiment;

FIG. 7 is a diagram showing a waveform example of a reference signal in servo data recorded in advance in each servo area 113 of the disk medium 11;

8 is a diagram showing an example of a head amplifier output waveform in a case where the reference signal in FIG. 7 is normally read by the MR head 12 and in a case where the reference signal is affected by deterioration of characteristics (magnetization reversal) of the MR head 12.

FIG. 9 is a view showing a part of a flowchart for describing a fourth read data error processing applicable in the embodiment;

FIG. 10 is an exemplary remaining part of the flowchart for explaining a fourth read data error processing applicable to the embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Lamp (predetermined location) 11 ... Disk medium (magnetic disk medium) 12 ... MR head 19 ... Head amplifier IC 20 ... Read / write IC 21 ... Gate array 23 ... Disk controller (HDC) 25 ... CPU (control device, characteristic) Deterioration detecting means) 111 Non-recording area (predetermined location) 112 Recording area 113 Servo area 191 Resistance measuring circuit (characteristic deterioration detecting means) 192 Current generating circuit 201 AGC circuit 202 Signal amplitude measuring circuit (characteristic deterioration) Detection means) 203: signal inversion discrimination circuit

Claims (8)

[Claims] In a magnetic disk drive provided with a magnetoresistive head using a magnetoresistive element for reading data from a magnetic disk medium, it is possible to detect whether the characteristics of the magnetoresistive head have deteriorated. Characteristic deterioration detecting means, a current generating circuit for generating a current to be supplied to the magnetoresistive head, and when a data error occurs in reading data by the magnetoresistive head, the characteristic deterioration detecting means In response to the detection of the presence of the characteristic deterioration of the head, the evacuation control means for retreating the head to a predetermined location other than the recording area on the magnetic disk medium or a predetermined location outside the magnetic disk medium, and the control of the evacuation control means Before performing the characteristic correction of the magnetoresistive head in a state where the head is retracted to the predetermined location, A magnetic disk drive comprising: a control device having refresh current generation control means for generating and outputting a refresh current to the head by the current generation circuit. 2. A magnetic disk medium in which a plurality of servo areas on which a servo data including a reference signal of a specific signal pattern is recorded are arranged at regular intervals on a recording surface radially from each center to each track. And a magnetoresistive head using a magnetoresistive element for reading data from the magnetic disk medium, and read from the servo area on the magnetic disk medium detected based on the reference signal. A magnetic disk drive for performing seek / positioning control of the head based on the servo data obtained, wherein a current generating circuit for generating a current to be supplied to the magnetoresistive head; and wherein the reference signal is read by the magnetoresistive head. A signal inversion identification circuit for identifying polarity inversion / non-inversion of the read reference signal at the time of reading; When a data error occurs in reading data by the resistance effect type head, the reference signal is read by the head and the polarity of the reference signal is inverted /
Reference signal inversion identification control means for identifying non-inversion by the signal inversion identification circuit, and the head when the polarity inversion of the reference signal read by the magnetoresistive head is identified by the signal inversion identification circuit. And a controller having a refresh current generation control means for generating and outputting a refresh current to the head by the current generation circuit in order to perform the characteristic correction. 3. The control device, when the refresh current is generated and output to the magnetoresistive head, causes the head to move to a predetermined location other than a recording area on the magnetic disk medium or to a position outside the magnetic disk medium. 3. The magnetic disk drive according to claim 2, further comprising a retreat control means for retreating to a predetermined location. 4. A magnetic disk medium in which a plurality of servo areas in which servo data including a reference signal of a specific signal pattern is recorded are arranged at regular intervals on a recording surface radially from the center of each track across each track. And a magnetoresistive head using a magnetoresistive element for reading data from the magnetic disk medium, and read from the servo area on the magnetic disk medium detected based on the reference signal. A magnetic disk drive for performing seek / positioning control of the head based on the servo data obtained, wherein a characteristic deterioration detecting means for detecting the presence or absence of characteristic deterioration of the magnetoresistive head; A current generating circuit that generates a current that flows when the reference signal is read by the magnetoresistive head. A signal inversion identification circuit for identifying the polarity inversion of the read reference signal, and when a data error occurs in reading data by the magnetoresistive head, the head reads the reference signal, Polarity inversion of reference signal /
Reference signal inversion identification control means for identifying non-inversion by the signal inversion identification circuit, wherein the characteristic is obtained when the polarity inversion of the reference signal read by the magnetoresistive head is identified by the signal inversion identification circuit. Refresh current generation control means for generating and outputting a refresh current to the head by the current generation circuit in order to correct the characteristics of the head irrespective of the detection result of the presence or absence of the characteristic deterioration of the head by the deterioration detection means; When a data error occurs during data reading by the magnetoresistive head, the characteristic deterioration detecting means detects the presence of characteristic deterioration of the head, and the polarity of the reference signal read by the magnetoresistive head is non-polar. When the inversion is identified by the signal inversion identification circuit, the magnetoresistive effect type head is used. And a control device having characteristic deterioration current generation control means for causing the current generation circuit to generate and output a characteristic deterioration current in a direction opposite to the refresh current for further deteriorating the characteristics of the head. Magnetic disk drive. 5. The control device, when the refresh current or the characteristic degradation current is generated and output to the magnetoresistive head, causes the head to move to a predetermined position other than a recording area on the magnetic disk medium or to the predetermined position. 5. The magnetic disk drive according to claim 4, further comprising a retreat control means for retreating to a predetermined position outside the magnetic disk medium. 6. A method for correcting characteristics of a magnetoresistive head in a magnetic disk device including a magnetoresistive head using a magnetoresistive element for reading data from a magnetic disk medium, the method comprising: When a data error occurs during data reading by the type head, it is determined whether or not there is characteristic deterioration of the head. When it is determined that there is characteristic deterioration of the magnetoresistive head, the head is replaced with the magnetic disk medium. The magnetic head is retracted to a predetermined location other than the upper recording area or a predetermined location outside the magnetic disk medium, and then a refresh current is supplied to the magnetoresistive head in order to correct the characteristics of the magnetoresistive head. And a magnetoresistive head characteristic correction method. 7. A magnetic disk medium in which a plurality of servo areas on which servo data including a reference signal of a specific signal pattern is recorded are arranged at regular intervals on a recording surface radially from the center of each track. And a magnetoresistive head using a magnetoresistive element for reading data from the magnetic disk medium, and read from the servo area on the magnetic disk medium detected based on the reference signal. A magnetic disk device for performing seek / positioning control of the head based on the servo data obtained, wherein a data error occurs in reading data by the magnetoresistive head, The head reads the reference signal to invert the polarity of the reference signal.
When the non-inversion is determined and the polarity inversion of the reference signal is determined, a refresh current is supplied to the corresponding magnetoresistive head in order to correct the characteristics of the head. Magnetoresistance effect type head characteristic correction method. 8. A magnetic disk medium in which a plurality of servo areas on which a servo data including a reference signal of a specific signal pattern is recorded are arranged at regular intervals on a recording surface radially from each center to each track. And a magnetoresistive head using a magnetoresistive element for reading data from the magnetic disk medium, and read from the servo area on the magnetic disk medium detected based on the reference signal. A magnetic disk device for performing seek / positioning control of the head based on the servo data obtained, wherein a data error occurs in reading data by the magnetoresistive head, Determine whether the characteristic of the head is deteriorated and read the reference signal by the head. In this case, the polarity inversion / non-inversion of the reference signal is determined. When the polarity inversion of the reference signal is determined, regardless of the determination result of the characteristic deterioration of the corresponding magnetoresistive head, Supplying a refresh current to the head in order to perform the characteristic correction; determining that the characteristic of the magnetoresistive head is deteriorated; and determining that the polarity of the reference signal is not inverted, the magnetoresistive head. The operation of supplying a characteristic deterioration current in the opposite direction to the refresh current for further deteriorating the characteristics of the reference signal to the head is repeated until the polarity inversion of the reference signal is confirmed. After confirming the polarity reversal of the above, a refresh current is supplied to the relevant magnetoresistive head in order to correct the characteristics of the head. A method for correcting a magneto-resistance effect type head characteristic.