JPH087203A - Driving method of mr head and hard-disk system - Google Patents

Abstract

PURPOSE: To enhance easily the stability of a magnetic domain of a MR head without carrying out complicated works such as disassembling and assembling etc. and reproduce data. CONSTITUTION: A drive device 28 is driven corresponding to a signal output from a controller body 40 of a HDC 30, and it records and reproduces data in a location where an access arm is pivoted at a specific angle. When data for this disk are recorded and reproduced, a bias current supplied to a reproduction element 21A of a magnetic head 20A having a MR effect is turned on/off only for a specific period by a reproduction control circuit 32A. Accordingly, as a direction of a magnetizing vector is changed within a specific period, a magnetic domain of the reproduction element 21A (MR element) is not unstable, but stabilized so that data from the disk can be reproduced stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving an MR head and a hard disk system, and more particularly to a method of driving an MR head when recording and reproducing information using the MR head having a magnetoresistive effect, and an MR head. A hard disk system equipped with.

[0002]

2. Description of the Related Art A hard disk drive unit (hereinafter referred to as HDD device) has been put into practical use as an information recording medium for recording a huge amount of information used in a computer or the like. This H
The DD device is provided with a plurality of magnetic recording disks (hereinafter, referred to as disks), and a reproducing / recording head (hereinafter, referred to as magnetic head) is positioned on a desired track defined on the disks, so that the disk is read. Information is being recorded or information is being reproduced from the disc.

This HDD device has a rotary actuator using a voice coil motor (VCM) for positioning the magnetic head at a predetermined position on the disk.
It is widely used because of its light weight, high speed, and low cost.
This rotary actuator has a rotating shaft outside the disk, and a magnetic head disposed at the tip is swiveled on the disk to position it at a predetermined position. The servo system is
For example, there is a sector servo system in which a pattern required for position control, a cylinder number and a sector number are recorded for each sector on each disk surface, and it is widely used particularly in small HDD devices.

In recent years, the capacity of HDD devices has been accelerating in consideration of the wide variety of processing in computers and the like. In order to increase the capacity of such an HDD device, there is a demand for a narrower track width and a corresponding reduction in the size of the magnetic head positioned on the track. As a magnetic head for
Considering that it is configured with a head.

In this MR head, a reproducing element and a recording element are formed independently, and the MR element having the MR effect as a reproducing element.
It is composed of an element and an inductive thin film head as a recording element. As is well known, the MR element has a magnetoresistive effect (MR
It is an element having an effect) and can detect a magnetic field in the vicinity of the MR element. This MR element requires a bias magnetic field in order to improve the linearity between the sensitivity and the changing magnetic field when detecting the magnetic field based on the change in the resistance value. As a general method for obtaining this bias magnetic field, a hard bias method using a permanent magnet film, a shunt bias method using a magnetic field generated by a bias current using a bias conductor, or detection of an MR element without using a bias conductor is used. There is a self-bias method (soft bias method) that uses a magnetic field generated from an electric current. By such a bias method, the magnetic domain in the reproducing element of the MR head can be controlled.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The MR head itself is reduced by reducing the gap length of the MR head along with the narrowing of the track width, which is a magnetic recording area for increasing the capacity of the device. For this reason, the instability of the magnetic domain of the MR head increases, and the external magnetic field and ESD / EOS (Electrical Overs
The output signal may become unstable due to external stress such as tress damage. The MR head in which the magnetic domain becomes unstable in this way can be restored to the original characteristics by performing initialization processing of the MR head again.

However, a direct access storage device (DASD, Direct Acc which is a storage device that can directly access data represented by a magnetic disk device such as an HDD device.
In the essStorage Device), when data cannot be reproduced due to instability of the magnetic domain of the MR head, the direct access storage device must be disassembled, the MR head must be taken out and initialized, and then reassembled.

According to the present invention, even if the magnetic domain of the MR head changes due to stress such as an external magnetic field or ESD / EOS, the magnetic domain of the MR head can be easily stabilized without performing complicated work such as disassembly and assembly. It is an object of the present invention to obtain a driving method of an MR head and a hard disk system capable of improving data reproduction and reproducing data.

[0009]

In order to achieve the above object, the invention according to claim 1 has a magnetoresistive effect and is provided with a bias magnetic field and reproduces information by using the magnetoresistive effect. With at least a reproducing element for
A method of driving the MR head when reproducing the information from an information recording disk by a head, characterized in that the information is reproduced after changing the bias magnetic field for a predetermined time.

According to a second aspect of the present invention, there is provided a reproducing element which has a magnetoresistive effect and is provided with a bias magnetic field and which reproduces information by using the magnetoresistive effect, and a recording element for recording the information. A method of driving the MR head at least when reproducing the information from an information recording disk by an MR head including a recording element, the information being reproduced after the bias magnetic field is changed for a predetermined time. Or that the information is recorded.

According to a third aspect of the present invention, there is provided the method of driving the MR head according to the first or second aspect, wherein the bias magnetic field is applied to the reproducing element by repeating application and non-application of the bias magnetic field. The feature is that the bias magnetic field is changed.

A fourth aspect of the present invention is the driving method of the MR head according to the first or second aspect, wherein a bias current is supplied to apply a bias magnetic field to the reproducing element, and the bias current is applied. It is characterized in that the bias magnetic field applied to the reproducing element is changed by changing the current value of the current.

According to a fifth aspect of the present invention, there is provided the method of driving the MR head according to the first or second aspect, wherein a bias current is supplied to apply a bias magnetic field to the reproducing element, and the bias current is applied. It is characterized in that the bias magnetic field applied to the reproducing element is changed by changing the polarity of the current.

According to a sixth aspect of the present invention, there is provided the method of driving the MR head according to the first or second aspect, wherein the reproducing element has a magnetoresistive effect and is supplied with a bias current. And a magnetized element that is magnetized by a bias current supplied to the magnetoresistive effect element and that applies a bias magnetic field to the magnetoresistive effect element by the magnetized magnetic field. There is.

According to a seventh aspect of the present invention, there is provided the MR head driving method according to the first or second aspect, wherein the reproducing element has a magnetoresistive effect element having a magnetoresistive effect and a bias current. And a magnetic field applying element for applying a bias magnetic field to the magnetoresistive effect element by the supplied bias current.

The hard disk system according to the invention of claim 8 has a reproducing element for reproducing information from the information recording disk by using the magnetoresistive effect and having a magnetoresistive effect and applying a bias magnetic field. Based on an output signal from the MR head, an MR head including a recording element for recording the information on the information recording disc, a magnetic field applying unit for applying the bias magnetic field to the reproducing element, An information recording / reproducing unit for reproducing the information and recording the information based on an input signal, and changing the bias magnetic field for a predetermined time when the information is recorded or reproduced by the information recording / reproducing unit. And controlling the magnetic field applying means to reproduce the information or record the information after changing the bias magnetic field. Comprises a control means for controlling, the.

[0017]

In the MR head driving method of the present invention, the MR head having the magnetoresistive effect and being provided with the bias magnetic field and at least the reproducing element for reproducing information by using the magnetoresistive effect, Information is reproduced from an information recording disk such as an HDD device. When reproducing this information, as described in claim 1, the information is reproduced after changing the bias magnetic field for a predetermined time. Even when an unstable magnetic domain is generated in the reproducing element due to the change of the bias magnetic field, the unstable magnetic domain is reduced, and the MR
A reproducing element having stable magnetic domains can be obtained without performing head initialization processing. As a result, defective reproduction of data or the like does not occur.

As described in claim 2, the MR
The head may have a magnetoresistive effect, a bias magnetic field is applied, a reproducing element for reproducing information by using the magnetoresistive effect, and a recording element for recording the information. The bias magnetic field is changed for a predetermined time when at least information is reproduced from an information recording disk such as an HDD device, that is, when information is reproduced or information is recorded. Therefore, it is possible to reduce unstable magnetic domains before recording or reproducing information,
Unstable magnetic domains, such as those that occur when recording or reproducing information, can be reduced before the next recording or reproducing of information. Therefore, at the time of recording or reproducing information, the reproducing element can be supplied in a state having stable magnetic domains. As a result, there is no possibility that a defective reproduction of data or the like will always occur.

The bias magnetic field applied to the reproducing element is
As described in claim 3, it can be changed by repeating application and non-application of the bias magnetic field. That is, if the magnetic field applied before information is recorded or reproduced is turned on and off, the bias magnetic field is changed for a predetermined time, and a reproducing element having a stable magnetic domain can be formed without performing initialization processing of the MR head. it can. Further, in order to generate the bias magnetic field applied to the MR head, it is general to supply the bias current. Therefore, as described in claim 4, as the bias magnetic field applied to the reproducing element, a bias current is supplied to apply the bias magnetic field to the reproducing element, and the current value of the bias current is changed. The bias magnetic field applied to the reproducing element may be changed. The current is
As is well known, since it has a polarity corresponding to the direction of current flow, a bias current is supplied to apply a bias magnetic field to the reproducing element, as described in claim 5.
By changing the polarity of the bias current, the bias magnetic field applied to the reproducing element can be changed with a simple configuration of reversing the polarity of the bias current.

The reproducing element of the MR head has a magnetoresistive effect element having a magnetoresistive effect and is supplied with a bias current, and a bias current supplied to the magnetoresistive effect element. It is possible to use a so-called soft bias type MR head that is composed of a magnetized element that is magnetized by the magnetized element and applies a bias magnetic field to the magnetoresistive effect element by the magnetized magnetic field. Further, the reproducing element of the MR head has a magnetoresistive effect element having a magnetoresistive effect, and a bias current is supplied, and a magnetic field is applied to the magnetoresistive effect element by the supplied bias current. It is possible to use a so-called shunt bias type MR head which is composed of a magnetic field applying element to be applied.

The driving method of the MR head can be realized by the hard disk system according to the eighth aspect.
This hard disk system has a magnetoresistive effect, a bias magnetic field is applied, and a reproducing element for reproducing information from an information recording disk by using the magnetoresistive effect, and the information to the information recording disk. An MR head including a recording element for recording is provided.
As the MR head, the so-called shunt bias type MR head and the so-called soft bias type MR head may be used. A bias magnetic field is applied to the reproducing element of this MR head by the magnetic field applying means. The information recording / reproducing means reproduces information from the MR head to which the bias magnetic field is applied, based on the output signal, and
Information is recorded based on the input signal. When recording or reproducing information by this information recording / reproducing means,
The control means controls the magnetic field applying means so as to change the bias magnetic field for a predetermined time, and controls the information reproduction or the information recording after changing the bias magnetic field. Therefore, the information recording / reproducing means has a simple and easy structure in which the bias magnetic field is changed for a predetermined time before recording or reproducing information, and reproducing having stable magnetic domains without performing initialization processing of the MR head. Can be an element. Therefore, it is possible to provide an HDD device in which unstable magnetic domains are reduced and reproduction failure of data or the like does not occur without taking out the MR head from the HDD device or performing initialization processing again.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. This embodiment uses a magnetic recording disk (disk)
In contrast, the present invention is applied to an HDD device 10 that positions a magnetic head by a sector servo method.

As shown in FIG. 2, the HD according to the first embodiment.
The D device 10 includes a drive device 14 that rotates the shaft 12 at high speed. A cylindrical support 16 is attached to the shaft 12 so that the axes of the shafts 12 are aligned with each other.
A plurality of (two in FIG. 2) disks 18A and 18B are attached to the outer peripheral surface of the support 16 at predetermined intervals. Each of the disks 18A and 18B has a disk shape with a predetermined thickness, is made of a hard material, and is coated with a magnetic material on both sides, so that both sides are recording surfaces. At the center of the disks 18A and 18B, holes having substantially the same diameter as the outer diameter of the support 16 are formed. The support 16 is inserted into the hole, and the disks 18A and 18B are fixed to the outer peripheral surface of the support 16. Therefore, when the shaft 12 is rotated by the drive device 14, the disk 1
8A and 18B are rotated integrally with the support 16.

On each recording surface of the disks 18A and 18B, a plurality of servo areas 50 are radially formed along the radial direction of the disk 18 as shown in FIG. 3, and the remaining areas are data track areas 52. ing. Servo area 5
In 0, a servo signal such as a burst pattern for indicating the arrangement direction of the data tracks is recorded, and a special code (a signalless area of about 1 μsec etc.) indicating the start of the pattern and an address of each data track are also recorded. The gray code (cyclic binary code) is recorded corresponding to the data track. At the end of the servo area 50 in the rotation direction, information for generating a sector pulse signal SP indicating the end of the servo area 50 (indicating the start of a sector) is recorded. In the data track area 52, a plurality of data tracks are formed concentrically along the radial direction at a pitch P, and information is written in each data track along the rotation direction of the disks 18A and 18B by a magnetic head described later. Be done.

The HDD device 10 includes a disk 18A,
Magnetic heads 20A to 20D having predetermined head gap widths and gap lengths provided corresponding to the respective recording surfaces of 18B.
It has. Each of the magnetic heads 20A to 20D functions as an MR head, and also has reproducing elements 21A to 21D for reading information and a recording element 19 for writing information.
A to 19D (see FIG. 1, details will be described later). Each of the magnetic heads 20A to 20D is attached to the tip of the corresponding access arm 22A to 22D and is held at a position slightly (for example, about 0.1 to 0.2 microns) away from the corresponding recording surface of the disks 18A and 18B. ing. The rear ends of the access arms 22A to 22D are attached to the support 24. The support portion 24 is attached to a drive device 28 via a shaft 26,
The access arms 22A to 22D are rotated by rotating the drive device 28 by a predetermined angle. When the access arms 22A to 22H are swung, the magnetic heads 20A to 20D move to the disks 18A, 1A.
It moves in the radial direction (see FIG. 3) on each recording surface of 8B and is positioned at a predetermined portion on the recording surface of the disks 18A to 18D.

The drive unit 28 is connected to a hard disk controller (hereinafter referred to as HDC) 30.
The HDC 30 includes magnetic heads 20A to 20A to
It is also connected to each of the 20Ds (see FIG. 1).

As shown in FIG. 1, the HDC 30 has a controller body 40. The controller body 40 is
Digital-to-analog converter (D / A) 28a, amplifier circuit (AMP) 28b, and voice coil motor (VCM)
It is connected to a drive unit 28 composed of 28c.
Therefore, after the digital signal output from the controller body 40 is converted into an analog signal in the D / A 28a and amplified by the AMP 28b at a predetermined magnification,
It is supplied to the VCM 28c. The VCM 28c rotates by a predetermined angle according to the supplied signal, and the access arm 22
A to 22D turn by a predetermined angle.

The controller body 40 is connected to the recording element 19A of the magnetic head 20A via a driver 34A for supplying a current for recording information, and also has a reproduction control circuit 32A for controlling a bias current. It is connected to the reproducing element 21A of the magnetic head 20A via. The reproduction control circuit 32A is a circuit that has an MR effect, supplies and changes a bias current to the reproduction element 21A for reading information, and detects a magnetic field according to the information recorded on the disc (FIG. 4 for details, see below). Similarly, the controller body 40 has a driver 34
The reproducing control circuit 3 is connected to the recording elements 19B to 19D of the magnetic heads 20B to 20D via B to 34D.
The reproducing elements 21B to 21D of the magnetic heads 20B to 20D are connected via 2B to 32D.

In this embodiment, in the reproduction control circuit 32A, the reproducing element 21 is changed by changing the bias current supplied to the reproducing element 21A of the magnetic head 20A.
The bias magnetic field applied to A is changed. The following five methods are available as specific methods for changing the bias magnetic field.

[Change of Bias Magnetic Field] Turning on / off the supply of bias current.

The current value Ix of the bias current is set to 0
From the initial value Ib to the predetermined current value Is.

The current value Ix of the bias current is set to an initial value I
Varying to a predetermined current value Iu between b and a current value 2Ib which is twice the initial value Ib.

The current value Ix of the bias current is 0
To a current value 2Ib that is twice the initial value Ib. That is, it is changed to a predetermined current value Is between the current value 0 and the initial value Ib, or is changed to a predetermined current value Iu between the initial value Ib and a current value 2Ib which is twice the initial value Ib. To do.

Reversing the supply direction of the bias current (reversing the polarity). The current value set as the current value 2Ib which is twice the initial value Ib is 2 times the initial value Ib.
The current value is not limited to twice, and an appropriate current value for obtaining the MR effect may be obtained in advance and the maximum value of the appropriate current value may be set.

The method of changing the bias magnetic field described above
You may make it change, combining a change method.

Next, a schematic configuration example for realizing the above method will be described. As shown in FIG. 4 (A), a reproduction control circuit 32A for realizing the changing method detects a magnetic field corresponding to information recorded on a reproducing driver 36A for supplying a bias current and a disc. It is composed of a detection circuit 38A and a switch circuit 42A.
The controller body 40 is connected to one terminal S _I of the switch circuit 42A via the driver 36A. The other terminal S _O is connected to the controller body 40 via the reproducing element 21A and the detection circuit 38A. Further, the switch circuit 32A includes a control end G connected to the controller body 40. The switch circuit 32A is configured by an analog switch circuit or the like that turns on and off according to a signal input from the control terminal G, and is turned off when a low level signal is input to the control terminal G, and a high level signal is input to the control terminal G. It is configured to turn on when it is performed. Therefore, the bias current is supplied when the switch circuit 32A is on, and is not supplied when it is off.

As shown in FIG. 4B, the changing method,
The reproduction control circuit 32A for realizing the above, is composed of a current changing circuit 44A and a detecting circuit 38A for changing the current value of the bias current supplied to the reproducing element 21A. The controller body 40 is a current changing circuit 44A
Connected to one side of the reproducing element 21A via
The other one of 1A is connected to the controller main body 40 via the detection circuit 38A. Further, the current changing circuit 44A includes a control end G connected to the controller body 40. The current changing circuit 44A is a current output type circuit composed of an amplifier circuit and the like, and outputs a current according to an input signal.

For example, two types of time constants of an amplifier circuit (not shown) are set in advance, and the current changing circuit 44A is configured to be switchable according to an input signal (for example, low level or high level) from the controller body 40. In the application of the changing method, the above-mentioned two types of time constants are obtained when the current value Ix of the bias current output from the current changing circuit 44A
The initial value Ib and the current value Is may be set to a predetermined current value Is between 0 and the initial value Ib. Therefore,
When a low level signal is input to the control terminal G, a bias current having an initial value Ib is output from the current changing circuit 44A, and when a high level signal is input to the control terminal G, the current changing circuit 4
A bias current having a current value Is is output from 4A.

Further, in the application of the changing method, the above-mentioned two types of time constants are set such that the current value Ix of the bias current output from the current changing circuit 44A is twice the initial value Ib and the initial value Ib to the initial value Ib. The current value Iu may be set to a predetermined current value Iu up to the current value 2Ib. Therefore, when a low level signal is input to the control terminal G, the current changing circuit 44
When a bias current having an initial value Ib is output from A and a high level signal is input to the control terminal G, the current changing circuit 44A
Will output a bias current of the current value Iu.

Further, when the changing method is applied, three types of time constants of an amplifier circuit (not shown) are predetermined. That is,
The current value Ix of the bias current output from the current changing circuit 44A is the initial value Ib, the predetermined current value Is between the current value 0 and the initial value Ib, and the initial value Ib to the initial value Ib.
A predetermined current value I up to a current value 2Ib which is twice as large as b
Determine to be u. In this case, when the low level signal is input to the control terminal G, the bias current having the initial value Ib is output from the current changing circuit 44A, and when the high level signal is input to the control terminal G, the current is changed. Circuit 4
From 4A, the bias current having the current value Is or the current value Iu may be switched so as to be output at predetermined time intervals and then output.

As shown in FIG. 4C, the reproduction control circuit 32A for realizing the changing method includes the reproduction driver 3
6A, a detection circuit 38A and a changeover switch circuit 46A. The controller body 40 is a driver 36
Is connected to the terminal S _D of the changeover switch circuit 46A via A, and is also changed over to the changeover switch circuit 4 via the detector 38A.
It is connected to the terminal S _C of 6A. The changeover switch circuit 46A has a control terminal G connected to the controller body 40.
It has. The changeover switch circuit 46A is a circuit for switching the path of two lines passing through the inside, and is turned off when a low level signal is input to the control terminal G, and the terminals S _A -S _D and S _B -S. Path through which _C conducts (Fig. 4
Solid line). Further, when a high level signal is input to the control terminal G, it is turned on and switched to a path (the imaginary line in FIG. 4) in which the terminals S _A -S _C and S _B -S _D conduct. The terminals S _A and S _B of the changeover switch circuit 46A are connected to both ends of the reproducing element 21A. Therefore, when the changeover switch circuit 46A is on, a bias current is supplied to the reproducing element 21A in a predetermined direction (direction of arrow L in FIG. 4), and when it is off, the reproducing element 21A is in reverse direction (direction of arrow R in FIG. 4). A bias current is supplied to. The changeover switch circuits 46A to 32D can be configured by an H bridge circuit or the like.

Since the reproduction control circuits 32B to 32D have the same structure as the reproduction control circuit 32A, detailed description thereof will be omitted.

Although the magnetic head 20A functions as an MR head, the reproducing element 21A and the recording element 19A are constructed independently. The recording element 19A is formed by sputtering an inductive thin film or the like. On the other hand, the reproducing element 21A has a magnetoresistive effect (MR effect) in which electric resistance is changed by a magnetic field or magnetization, as described later.
In the present embodiment, the linearity between the sensitivity and the changing magnetic field when the magnetic field is detected by the change of the resistance value by applying the bias magnetic field by the soft bias method is improved, and the magnetic field in the vicinity of the reproducing element is included. It is something to detect. The magnetic heads 20B to 20D are the same as the magnetic head 2
The magnetic head 20A has the same configuration as that of the magnetic head 20A.
Will be described, and detailed description of the magnetic heads 20B to 20D will be omitted.

As shown in FIG. 5, the reproducing element 21A has M
Substantially plate-shaped MR element 62 having R effect and soft magnetism (film)
Material (soft Adjacent Layer, hereinafter referred to as SAL)
64 is provided. In each of the both ends of the MR element 62,
The lead wire 66 is attached, and the lead wire 66 is attached.
Are connected to the HDC 30. The SAL 64 is formed by laminating it in parallel with the MR element 62, and each of them is arranged in a horizontal position with respect to the disk 18A. Since the SAL 64 is a soft magnetic material, the MR element 62
It is magnetized by the current supplied to it. A bias magnetic field is applied to the MR element 62 by the magnetized magnetic field of the SAL 64.

As shown in FIG. 6, the MR of the reproducing element 21A is
When no current is supplied to the element 62, the SAL 64 is not magnetized, so the direction of the magnetization vector is the manufacturing direction (arrow H _{0 in} FIG. 6). A predetermined current as a bias current to the MR element 62 in a predetermined direction (indicated by a white arrow I in FIG. 6)
, A vertical magnetic field in a predetermined direction (direction of arrow U in FIG. 6) is generated in the SAL 64 by the predetermined current supplied to the MR element 62. The magnetic field of this SAL 64 is the MR element 62
To be applied as a bias magnetic field, the orientation of the magnetization vector in the MR element 62 is (in the arrow H _D direction in FIG. 6) varies.

On the other hand, when the direction (polarity) of the current supplied to the MR element 62 is reversed (the direction opposite to the white arrow I direction in FIG. 6), the SAL 64 moves in the opposite direction (direction opposite to the arrow U direction in FIG. 6). Vertical magnetic field is generated. Therefore, the direction of the magnetization vector in the MR element 62 changes in the opposite direction (direction of arrow H _{U in} FIG. 6). Therefore, by reversing the direction of the vertical magnetic field applied to the MR element 62 by the SAL 64, the direction of the magnetization vector in the MR element 62 is changed from the direction H ₀ when the bias current is not supplied to the bias supplied to the MR element 62. It will fluctuate in the direction H _U or the direction H _D depending on the direction of the current.

Next, the operation of this embodiment will be described with reference to the flowcharts of FIGS. 7 and 8 together with the processing in the HDC 30 for eliminating the unstable magnetic domain of the MR head.
From the host computer or the like (not shown) to the disk 18
When the processing for recording / reproducing information to / from A is instructed, FIG.
The recording / reproducing processing routine shown in is executed. In step 100 of FIG. 7, a recovery process described later is executed. When this recovery processing is completed, the recording / reproduction processing mode (R / W mode) is shifted to step 150, and the recording processing or the reproduction processing of the information for the disc 18A is executed.

When the recovery processing of FIG. 8 is executed, in step 102, a high level signal is output to the current changing circuit 44A in order to change the bias magnetic field applied to the reproducing element 21A of the magnetic head 20A. As a result, the bias current output from the current changing circuit 44A is changed from the initial value Ib, and the bias magnetic field applied to the reproducing element 21A is changed. When the high level signal is output for a predetermined time (for example, 10 ms) which is set in advance (step 104), the low level signal is output to the current changing circuit 44A in order to return the bias current to the initial value in step 106. This routine ends.

In this way, since the bias current is changed from the initial value Ib, the bias magnetic field applied to the reproducing element 21A is changed. Therefore, the direction of the magnetization vector changes within a predetermined time. Therefore, the magnetic domain of the reproducing element, particularly the MR element is not unstable, and the information can be stably reproduced from the disc.

The change of the bias magnetic field will be described in detail. As shown in FIG. 9A, the predetermined bias current Ib
And when the reproducing element 21A is in a stable state,
An unstable magnetic domain does not occur in the reproducing element 21A. Reproducing element 2 when this predetermined bias current Ib is supplied
The direction of the magnetization vector in 1A is an angle that forms a predetermined angle θb from the direction of the magnetization vector when the bias current is not supplied (see FIG. 9C). This reproducing element 21A
External magnetic field and ESD / EOS (Electrical Overstress
When external stress such as (Damage) is applied under load, an unstable magnetic domain is generated (see FIG. 9B). This unstable magnetic domain causes the output signal of the magnetic head to become unstable.

Therefore, in the changing method described above,
By outputting a high level signal to the control terminal G (see FIG. 4A) and changing the supply of the bias current from the non-supply (the state of FIG. 9A and the state of FIG. 9C), Since the direction of the magnetization vector is changed as in the case where the direction of the magnetization vector is continuously changed to demagnetize, the unstable magnetic domain can be eliminated.

In the changing method, the control end G (see FIG.
By outputting a high level signal to (B) and changing the bias current from the initial value Ib to the current value Is (0 <Is <Ib) (the state of FIG. 9A and the state of FIG. 9D).
State) and the direction of the magnetization vector is changed, an unstable magnetic domain can be eliminated. The direction of the magnetization vector in the reproducing element 21A when the current value Is is supplied forms an angle θ ₁ from the direction of the magnetization vector when the bias current is not supplied (see FIG. 9C) (0 < θ ₁ <θ b). In the changing method, the bias current is changed from the initial value Ib to the current value Iu (Ib <Iu <2Ib) (the state of FIG. 9A and the state of FIG. 9A).
(State (E)), since the direction of the magnetization vector is changed, an unstable magnetic domain can be eliminated. The direction of the magnetization vector in the reproducing element 21A when the current value Iu is supplied is the same as when the bias current is not supplied (see FIG. 9).
The angle θ ₂ is formed from the direction of the magnetization vector (see (C)) (0 <θ ₂ <θb). In the changing method, the bias current is changed from the initial value Ib to the current value Ix (Is <Ix <
Iu) (state of FIG. 9 (A), state of FIG. 9 (D), state of FIG. 9 (E)) changes the direction of the magnetization vector, so unstable magnetic domains are generated. It can be resolved. That is, it is changed to a predetermined current value Is between the current value 0 and the initial value Ib, or is changed to a predetermined current value Iu between the initial value Ib and a current value 2Ib which is twice the initial value Ib. By doing so, the bias current can be selectively supplied.

In the changing method, if the current value Is or the current value Iu set is set to a current value capable of obtaining a bias magnetic field sufficient for reproduction, the initial value I
Instead of returning to b, the recording / reproducing process may be directly performed (current value Is or current value Iu). That is, the above step 106 may be omitted. In this case, in step 102 of FIG. 8, the initial value Ib is changed to the current value Ib.
s or the current value Iu, the current value Is or the current value Iu may be changed to the current value that is currently set to the initial value Ib.

In the changing method, the polarity of the bias current is inverted by outputting a high level signal to the control terminal G (see FIG. 4C). That is, since the direction of the magnetization vector is changed by changing the bias current from the initial value Ib to the current value −Ib (state of FIG. 9A and state of FIG. 9F), it is unstable. It is possible to eliminate the magnetic domain. The direction of the magnetization vector in the reproducing element 21A when the polarity of the bias current is reversed forms an angle θ ₃ with the direction of the magnetization vector when the bias current is not supplied (θ ₃ = −θb).

The above-mentioned recovery process is not limited to being executed before the recording / reproducing process, but may be executed periodically. Alternatively, it may be executed according to an instruction from an operator or a host computer.

As described above, in this embodiment, when the bias magnetic field is applied to the MR head, the instability of the magnetic domain can be eliminated by changing the direction of the bias magnetic field. Therefore, the HDD device is disassembled. It is possible to provide a magnetic head with stable magnetic domains without initializing the magnetic head. Therefore, in reproduction of information, reproduction failure does not occur.

In the above, the change of the bias magnetic field corresponding to the changing methods (1) to (4) has been described. Next, these modified examples will be described. In the recording / reproducing processing mode (step 150), there are recording processing and reproducing processing, but it is mainly the reproducing processing that requires the bias magnetic field. Therefore, in the following description, the case where the bias magnetic field in the reproducing process is changed by changing the bias current supplied at the time of switching from the recording process to the reproducing process will be described.

In the modified example A, as shown in FIG. 12, the current value Ix of the bias current is changed from the current value 0 in the recording process to the current value used in the reproducing process (initial value Ib, for example,
After changing the current value (current value Iu, for example, 10 mA) increased by 10% to 50% (8.5 mA) for a predetermined time t, then changing to the current value (initial value Ib) used in the regeneration process. Changes the bias field. In this case, to the control terminal G of the current changing circuit 44A of FIG.
After the current value Iu is supplied at the predetermined time t, the current value Ib is
The control signal may be input so as to be supplied. The predetermined time t is preferably set to be less than the time within the time lag at which the recording process is switched to the reproducing process. By doing so, the direction of the magnetization vector is changed before the reproduction process is started, so that at the time the reproduction process is started, the reproduction process is performed in a stable state in which an unstable magnetic domain is eliminated. can do.

The modified example B is an application of the modified example A, and is a method of changing the bias magnetic field that can simplify the device configuration. That is, as shown in FIG. 13, a predetermined bias current (for example, a current value Iu) is supplied at the time of shifting to the regeneration process, and a predetermined bias current (at a time t corresponding to the time constant τ of an attenuator (not shown) is supplied ( For example, the bias magnetic field is changed by supplying the bias current that is gradually attenuated to the current value Ib). In this case, the reproduction control circuit 32A shown in FIG. 4A may be replaced with the switch circuit 42A and may be configured by an attenuating circuit (not shown) having a predetermined time constant τ.
The damping circuit (not shown) is provided in the controller body 4
No connection to 0 is required. As described above, in the modified example B, the CPU does not perform a special process for changing the bias magnetic field, the bias magnetic field is changed by simply supplying the bias current, and the apparatus only adds an attenuation circuit. The configuration is simple. In addition, at the time of starting the supply of the bias current, an overshoot in which a current exceeding the current value set for supply is usually generated, so even if this overshoot occurs, this example Works effectively.

The modification C is to perform the attenuation of the modification B stepwise, and as shown in FIG. 14, a predetermined bias current (for example, current value Iu) is supplied at the time of shifting to the regeneration process. After that, a predetermined bias current (for example, current value I
The bias magnetic field is changed by gradually attenuating to b) and supplying the bias current. In this case, the current changing circuit 44A shown in FIG. 4B may be configured so that the control signal is input stepwise to the control terminal G so that the bias currents having a plurality of current values can be output. In addition, the control signal is a time (t ₁ , t ₂ ,
..., t _n ), and output so as to change discretely.
As a result, the current value gradually changes from the current value Iu to the current value Iu.
The bias magnetic field is changed by changing to b.

The modification D is a combination of the above, and as shown in FIG. 15, the current value Iu is maintained during the division time t ₁ obtained by dividing the predetermined time t into a plurality of times, and thereafter, the bias value is gradually biased. Attenuating the current modifies the bias field. In this case, the reproduction control circuit 32 shown in FIG.
The switch circuit 42A may be configured to include a switch circuit capable of switching the switch circuit 42A between a contact via an attenuating circuit (not shown) having a predetermined time constant τ and a contact passing therethrough. A current passes through the control terminal G as it is during the division time t ₁ , and then a control signal is input so as to pass through the attenuation circuit.

In the modification E, the bias magnetic field is changed by alternatingly changing the current value of the bias current.
That is, as shown in FIG. 16, from a predetermined maximum amplitude to a predetermined current value (for example, current value Ib), the current value fluctuates in an alternating manner and is attenuated and stabilized. The bias magnetic field is changed by the variation of the alternating current value of the bias current. In this case, the reproduction control circuit 32 shown in FIG.
Instead of the switch circuit 42A, A may be formed by an AC attenuation circuit (not shown) having a predetermined time constant τ and having the characteristics shown in FIG.

Modification F has been described in Modification B after the polarity of the bias current is reversed, as shown in FIG.
The bias magnetic field is changed by gradually attenuating the bias current from a predetermined bias current (for example, current value Iu) to a predetermined bias current (for example, current value Ib). In this case, the changeover switch circuit 4 shown in FIG.
The attenuation circuit (not shown) may be provided on one side of 6A.

In the modification G, as shown in FIG. 18, the bias magnetic field is changed by attenuating the current value of the bias current while changing the polarity reversal of the bias current in an alternating manner. In this case, the changeover switch circuit 46 shown in FIG.
It suffices to provide the above-mentioned AC attenuating circuit in A to configure.

The stability of magnetic domains in the magnetic head has a correlation with the distortion rate of the reproduced signal. Therefore, the distortion rate of the output signal of the magnetic head is obtained from 2OLOG (F1 / F2). However, F1: the signal level of the signal frequency of the external magnetic field,
F2: The signal level of the second harmonic of the F1 signal. With respect to the change in the distortion rate 2OLOG (F1 / F2) of the magnetic head signal, a slight change in the reproduced signal waveform can be accurately measured.

FIG. 10 shows the signal change characteristic of the magnetic head output when the bias current is repeatedly inverted for a predetermined time (10 ms) by the above changing method. In the figure, time is set on the horizontal axis and the distortion rate of the magnetic head is set on the vertical axis. In the initial stage of inverting the polarity of the bias current, which is the restoration process described above (for a predetermined time,
10 ms), the strain rate fluctuates drastically due to the supply of the bias current in the reverse direction. However, by repeating the polarity reversal of the bias current, the variation in the strain rate becomes small, and the stable magnetic domain structure was reconfigured. To be understood.

Next, a second embodiment will be described. In the above embodiment, an example in which the recovery process is performed every time the information recording / reproducing process for the disk 18A is performed, but in the present embodiment, the recovery process is performed only when the magnetic domain of the magnetic head becomes unstable. It is a thing. Since the present embodiment has the same configuration as the above embodiment, the same portions are denoted by the same reference numerals, detailed description thereof will be omitted, and different portions will be described below.

For example, when a host computer (not shown) or the like issues a recording / reproducing process of information to / from the disc 18A, a recording / reproducing process routine shown in FIG. 11 is executed. In step 200 of FIG. 11, a magnetic head performance deterioration detection process is performed. That is, the occurrence of the instability of the magnetic domain of the magnetic head is detected by using the correlation between the stability of the magnetic domain in the magnetic head and the distortion rate of the reproduction signal described above. This detection can be obtained by statistically calculating the standard deviation, variance, maximum value, minimum value, etc. of the signal output when the bias current is repeatedly inverted a predetermined number of times as in the above embodiment. In the next step 210, it is determined whether or not performance degradation has occurred as a result of the detection processing in step 200. If the determination is affirmative, in step 100 the recovery processing is performed in the same manner as above. On the other hand, in the case of a negative determination, since the magnetic domain of the magnetic head is stable, the process proceeds to step 150 as it is, and shifts to the recording / reproducing processing mode (R / W mode) to record or reproduce information on the disk 18A. Is executed to end this routine.

As described above, in the present embodiment, since the performance deterioration of the magnetic head is detected and it is determined whether or not the restoration processing is performed based on the detection result, the magnetic head that needs the restoration processing. Optimal restoration processing can be performed only in the state of. Therefore, the CPU load of the restoration process is reduced.

Although the embodiments of the present invention have been described above, the embodiments of the present invention have various technical aspects as described below in addition to the requirements described in the claims. The MR head driving method according to claim 1, wherein a magnetic domain of the reproducing element is detected, and it is determined whether or not the detected magnetic domain is unstable. When it is determined that the magnetic domain is unstable, the bias magnetic field is applied for a predetermined time. It is characterized in that the information is reproduced only after being changed.

[0071]

As described above, according to the driving method of the MR head of the present invention, even when an unstable magnetic domain is generated in the reproducing element, the unstable magnetic domain is reduced by the change of the bias magnetic field. Therefore, there is an effect that a defective reproduction such as data due to an unstable magnetic domain does not occur.

Further, according to the hard disk system of the present invention, the unstable magnetic domain is reduced without taking out the MR head or performing the initialization process again, and the reproduction failure of data or the like does not occur and the information is recorded. There is an effect that it is possible to easily provide an apparatus capable of continuously performing recording and reproduction.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration around a hard disk controller of an HDD device to which the present invention can be applied.

FIG. 2 is a block diagram showing a schematic configuration of an HDD device to which the present invention can be applied.

FIG. 3 is an image diagram showing a disk of an HDD device.

FIG. 4 is a conceptual configuration diagram of a reproduction control circuit, in which (A) is a bias current on / off, (B) is a change in bias current,
(C) shows the polarity change of the bias current.

FIG. 5 is a conceptual perspective view of a reproducing element using a soft bias method.

FIG. 6 is an explanatory diagram for explaining a bias magnetic field in the reproducing element.

FIG. 7 is a flowchart showing a processing flow for changing and applying a bias magnetic field during information recording / reproduction according to the first embodiment.

FIG. 8 is a flowchart showing details of a restoration process.

9A and 9B are explanatory views for explaining the direction of the bias magnetic field of the reproducing element by the bias current, FIG. 9A is an image diagram showing an unstable magnetic domain when the bias current is supplied in a predetermined direction, and FIG. ) Is when the bias current is not supplied,
(D) is an image diagram showing the direction of the bias magnetic field when supplying a current smaller than the initial value, (E) when supplying a current larger than the initial value, and (F) when supplying a reverse bias current.

FIG. 10 is a characteristic diagram showing a signal change characteristic of a magnetic head.

FIG. 11 is a flowchart showing the flow of processing for changing and applying a bias magnetic field during information recording / reproduction according to the second embodiment.

FIG. 12 is a modification example A for changing and giving a bias magnetic field.
FIG. 6 is a diagram showing a bias current characteristic according to FIG.

FIG. 13 is a modification B for changing and imparting a bias magnetic field.
FIG. 6 is a diagram showing a bias current characteristic according to FIG.

FIG. 14 is a modification C for changing and imparting a bias magnetic field.
FIG. 6 is a diagram showing a bias current characteristic according to FIG.

FIG. 15 is a modification D for changing and giving a bias magnetic field.
FIG. 6 is a diagram showing a bias current characteristic according to FIG.

FIG. 16 is a modification E for changing and giving a bias magnetic field.
FIG. 6 is a diagram showing a bias current characteristic according to FIG.

FIG. 17 is a modification F for changing and giving a bias magnetic field.
FIG. 6 is a diagram showing a bias current characteristic according to FIG.

FIG. 18 is a modification G for changing and imparting a bias magnetic field.
FIG. 6 is a diagram showing a bias current characteristic according to FIG.

[Explanation of symbols]

 10 hard disk device 18A disk 19A recording element 20A magnetic head 21A reproducing element 22A access arm 30 hard disk controller 32A reproducing control circuit 40 controller body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Uchida 1623 Shimotsuruma, Yamato-shi, Kanagawa 14 Japan AIBM Co., Ltd. Tokyo Research Laboratories (72) Inventor, Takashi Toyooka, Yamato-shi, Kanagawa 1623 Tsuruma 14 Japan AI Laboratories, Tokyo Research Laboratories (72) Inventor Takao Matsui 1 Kirihara Town, Fujisawa City, Kanagawa Japan IBM Japan Ltd. Fujisawa Office (72) Inventor Aoki Tatsuji 1 Kirihara-cho, Fujisawa-shi, Kanagawa Japan IBM Japan Ltd. Fujisawa Plant (72) Inventor Yasuhiro Iihara 1-Kirihara-cho, Fujisawa City, Kanagawa Japan IBM Japan Ltd. Fujisawa Plant (72) Invention Person Kazunari Tsuchimoto 1 Kirihara Town, Fujisawa City, Kanagawa Prefecture IBM Japan, Ltd. Fujisawa Plant (72) Inventor Yutaka Ozawa Fujisawa, Kanagawa Prefecture Kirihara-cho, address IBM Japan, Ltd. Fujisawa plant

Claims (8)

[Claims] 1. An MR head having a magnetoresistive effect, to which a bias magnetic field is applied, and at least a reproducing element for reproducing information by using the magnetoresistive effect, by means of an MR head. A method of driving the MR head when reproducing, wherein the information is reproduced after the bias magnetic field is changed for a predetermined time. 2. A reproducing element for reproducing information by using the magnetoresistive effect while having a magnetoresistive effect and applying a bias magnetic field, and a recording element for recording the information. When the MR head reproduces at least the information from the information recording disk, the MR
A method for driving a head, comprising: reproducing the information or recording the information after changing the bias magnetic field for a predetermined time. 3. The method of driving an MR head according to claim 1, wherein the bias magnetic field applied to the reproducing element is changed by repeating application and non-application of the bias magnetic field. 4. A bias current is supplied to apply a bias magnetic field to the reproducing element, and the bias magnetic field applied to the reproducing element is changed by changing the current value of the bias current. The method of driving an MR head according to claim 1 or 2. 5. A bias current is supplied to apply a bias magnetic field to the reproducing element, and the bias magnetic field applied to the reproducing element is changed by changing the polarity of the bias current. The method of driving an MR head according to claim 1 or 2. 6. The reproducing element has a magnetoresistive effect and is supplied with a bias current, and is magnetized by the bias current supplied to the magnetoresistive element and the magnetized magnetic field. 3. The method of driving an MR head according to claim 1, further comprising: a magnetized element that applies a bias magnetic field to the magnetoresistive effect element. 7. The reproducing element includes a magnetoresistive effect element having a magnetoresistive effect, and a magnetic field applying element which is supplied with a bias current and applies a bias magnetic field to the magnetoresistive effect element by the supplied bias current. The method of driving an MR head according to claim 1 or 2, wherein: 8. A reproducing element which has a magnetoresistive effect and is provided with a bias magnetic field and reproduces information from the information recording disk by using the magnetoresistive effect, and the information to the information recording disk. An MR head including a recording element for recording, a magnetic field applying unit for applying the bias magnetic field to the reproducing element, and reproducing and inputting the information based on an output signal from the MR head. Information recording / reproducing means for recording the information based on a signal, and controlling the magnetic field applying means so as to change the bias magnetic field for a predetermined time when recording or reproducing the information by the information recording / reproducing means, A hard disk provided with a control means for controlling the reproduction of the information or the recording of the information after changing the bias magnetic field. Stem.