JP3313615B2 - Magnetic recording / reproducing apparatus and reproducing head using magnetoresistive element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus such as a hard disk drive and a magnetic resistance element.
Related to playback head.

[0002]

2. Description of the Related Art Magnetic recording / reproducing devices, for example, hard disk devices, are widely used as large-capacity random-access external storage devices for computers. Hard disk drives are increasingly required to have higher recording densities in order to increase the storage capacity, and research and development are being carried out in various fields to meet this demand.

Generally, in a hard disk drive, a plurality of magnetic disks each having a magnetic layer provided on a non-magnetic substrate are stacked and mounted on one rotating shaft, and a recording / reproducing head is mounted on an arm and each disk surface is mounted. The arm is moved in the radial direction of the disk by the actuator to perform the positioning of the head, that is, the seek operation. When recording and reproducing signals,
The head does not directly contact the disk surface rotating at high speed,
It is arranged so as to access a desired position on the disk surface while slightly floating. Then, a signal is recorded by a head on a concentric track on the disk surface, or the recorded signal is reproduced.

In such a hard disk device,
In order to meet the demand for large storage capacity, the recording density should be increased by increasing the linear recording density of the disk, that is, the recording density in the track length direction, or by increasing the track density by narrowing the track width. Attempts have been made so far. In recent years, in order to further increase the recording density, research and development of contact recording, in which the head is made to fly extremely low or the head is almost brought into contact with a recording medium to perform recording / reproduction, have been actively performed.

On the other hand, active heads typified by MR heads utilizing the magnetoresistance effect have been actively developed in order to increase the sensitivity of signal reproduction. An MR head is a head that converts a magnetic flux from a recording medium into an electric signal by utilizing the property that the electric resistance of a soft magnetic material such as permalloy is changed by an external magnetic field. The read sensitivity of this head is proportional to the magnitude of the sense current flowing through the MR element in order to convert a change in the electrical resistance of the MR element made of a soft magnetic material into a voltage change. There is a feature that a large reproduction output can be obtained even in a small case. Also, by utilizing the feature that the reproduction output of the MR head is large, it is possible to narrow the track width and increase the track density.

In many cases, a reproducing head composed of an MR head is mounted on a head slider as a composite head integrated with a recording head composed of an induction type head at a predetermined distance in a track direction. The composite head is moved in the radial direction of the disk by the rotary actuator via the head slider, and the positioning operation to the target track, that is, the seek operation is performed as described above. In this case, a track shift occurs between the recording head and the reproducing head during the seek operation due to the interval existing in the track direction between the recording head and the reproducing head. Here, the track deviation means that the relative position between the head and the track differs between the recording head and the reproducing head.

[0007] Regarding the mechanism of this track deviation,
This will be described with reference to FIG. FIGS. 19A and 19B are diagrams schematically showing a state in which the composite head moved by the rotary actuator is located on the inner track and the outer track on the magnetic disk, respectively. As shown in the figure, when the composite head is moved using the rotary actuator, the angle difference between the head direction (azimuth direction) and the track direction, the so-called skew angle, changes depending on the track radius position where the head is located. I do. In the example of FIGS. 19A and 19B, the skew angle θ is negative on the inner peripheral side and positive on the outer peripheral side. Such a change in the skew angle due to the track radius position directly appears as a track shift between the recording head and the reproducing head. This track shift increases particularly as the track pitch becomes narrower, and poses a problem in performing correct reproduction.

Further, when the track width is reduced to increase the track density, it is necessary to increase the positioning accuracy of the recording head and the reproducing head in the track width direction. But,
When the track is narrowed, the alignment tolerance between the recording head and the reproducing head becomes relatively large in terms of the accuracy of the manufacturing process, which is a major obstacle to increasing the track density.

Further, a two-stage control type head drive mechanism using a rotary actuator as a coarse actuator and a mechanical microactuator as a fine actuator has been proposed. With this head drive mechanism, the composite head allows the recording head to ride on the track during recording,
At the time of reproduction, the reproduction head is controlled so as to ride on the track. Therefore, when recording and reproduction are frequently repeated, the entire composite head must be driven frequently, and the time required for accurately settling the desired recording head or reproduction head on the target track increases. I will.

Further, when the spacing between the head and the medium becomes extremely small and the two come into contact with each other, the contact force is applied as a disturbance to the microactuator, so that the head driving mechanism can exhibit a sufficient function. Therefore, there arises a problem that high-accuracy tracking control cannot be performed.

[0011]

As described above, in a magnetic recording / reproducing apparatus using a composite head, there is an inherent problem of track deviation, and the track deviation causes a decrease in reproduction output, resulting in a decrease in track output. This hinders the narrowing of the pitch and the density of the track.

[0012] It is an object of the present invention is to realize a narrowing and densification of the track of the track pitch, and a large reproduced output magnetic recording and reproducing apparatus capable of obtaining a and
An object of the present invention is to provide a reproducing head using a magnetoresistive element .

[0013]

The above object can be achieved by the following magnetic recording / reproducing apparatus. (1) A signal is written on a magnetic recording medium along a predetermined track.
A magnetic recording head and a spin-valve magnetic resistor
A resistance element and a spin valve type magnetoresistive element.
Applying a bias magnetic field to the spin valve type magnetoresistive element
The sensitivity distribution of the spin-valve magnetoresistive element is
Magnetic field applying means for changing the width of the rack.
A reproduction head for reproducing signals recorded on a magnetic recording medium.
And the bias magnetic field by the spin-valve magnetoresistive
Means for applying an external control signal for applying to the element to the magnetic field
Recording means comprising:
Playback device. (2) A signal is written on a magnetic recording medium along a predetermined track.
A magnetic recording head and a spin-valve magnetic resistor
Due to the anti-element and the shunt bias effect.
The bias magnetic field is applied to
The sensitivity distribution of the valve type magnetoresistive element
The current for changing the direction is
Means for flowing the resistance element itself,
A reproducing head for reproducing a recorded signal;
To apply a magnetic field to the spin-valve magnetoresistive element
Control means for providing an external control signal to the magnetic field applying means,
A magnetic recording and reproducing device comprising: (3) A signal is written on a magnetic recording medium along a predetermined track.
A magnetic recording head and a spin-valve magnetic resistor
A signal recorded on the magnetic recording medium.
A reproducing head for reproducing, and the spin valve type magnetoresistive element
The track, the recording head and
Current is supplied according to the positional relationship with the read head.
And a conductive member provided with the magnetic recording medium.
Raw equipment. (4) A signal is written on a magnetic recording medium along a predetermined track.
A magnetic recording head and a spin-valve magnetic resistor
Resistance element and this spin valve type magnetoresistive element
And a bias magnetic field is applied to the spin valve type magnetoresistive element.
Means for applying a bias magnetic field to be applied.
Sensitivity distribution between the read head and the write head.
Spacing and the angle between the orientation of the playback head and the longitudinal direction of the track
A reproducing head member that changes on the basis of the degree difference.
A magnetic recording / reproducing apparatus characterized by the above-mentioned. (5) A signal is written on a magnetic recording medium along a predetermined track.
The recording head that records magnetically and the sensitivity distribution
A spin-valve magnetoresistive element that changes in the width direction
The spin-valve type magnetoresistive
The current for applying a bias magnetic field to the device is
Means for flowing into the valve-type magnetoresistive element itself.
Current flowing through the spin-valve magnetoresistive element itself by the step
Is the distance between the read head and the recording head and the read head
Stipulated based on the angle difference between the direction of the track and the longitudinal direction of the track
Magnetic head, comprising: a reproducing head;
Recording and playback device. (6) Reproduce a signal recorded on a track of a magnetic recording medium
Using a spin-valve type magnetoresistive element for reading
In the head, the first and second magnetic layers, and the first and second magnetic layers
A non-magnetic conductive layer provided between the two magnetic layers,
The sensitivity distribution changes according to the track width position,
The magnetization directions of the first and second magnetic layers are along the track width direction.
The first magnetic layer is aligned so as to be orthogonal at a predetermined position.
And the second magnetic layer is non-uniformly magnetized.
A reproducing head. Thus, in the present invention
Is a reproduction head of a composite head,
GMR using pin valve type magnetoresistive element (GMR element)
Using the GMR head and the sensitivity distribution of the GMR head
By moving the mind, using the GMR head
To obtain a large playback output and move the center of the sensitivity distribution
The calling of the cross-talk between the track each other even as the
Narrow track pitch without increasing rawness
And achieve a higher track density. The present invention provides a GMR
The head has a symmetric sensitivity characteristic and moves the center of the sensitivity distribution
Characteristics, without expanding the tail of the characteristic curve.
There is a focus on the movement of the entire curve. On the other hand,
Of sensitivity distribution to the spin-valve magnetoresistive element
By controlling the magnetic field, the conventional mechanical
Servo band, that is, head drive compared to the head drive mechanism
The frequency band can be made very high. Sand
In other words, conventional rotary actuators and microactuators
In the case of mechanical actuators such as eta
Servo driving beyond the natural frequency of the z-order is impossible.
I can't. On the other hand, as in the present invention, the reproducing head is magnetically reproduced.
In the method that controls movement of the sensitivity distribution of the
The driving target of the data function is the magnetic characteristics of the read head itself.
With a certain sensitivity distribution, a mechanical type that drives the read head itself
Unlike actuators, the driven object has no mass
One digit compared to using only mechanical actuators
Thus, it becomes possible to perform servo driving at a high frequency.
As a result, very responsive head positioning control is achieved.
It is possible, even if recording and playback are repeated frequently.
Position the desired recording or playback head on the target track.
The time required for sure settling is reduced. Further
In this way, the sensitivity distribution of the read head is magnetically moved
The mechanical contact between the head and the media
Even if disturbance is applied to the head, the mechanical actuator
The head drive is not affected as in
Head positioning control can be performed.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the preferred embodiment of the present invention, the principle of the present invention will be described. As mentioned earlier,
The track shift between the recording head and the reproducing head that occurs during the seek operation is that the reproducing head is not located at an appropriate position on the track. The problem of the track deviation lowers the reproduction output and prevents the track pitch from becoming narrower and the track from having a higher density.

In order to solve the problem of track deviation, there is provided a means for preventing a decrease in reproduction output by moving the sensitivity distribution of the reproducing head even if the reproducing head is not located at an appropriate position on the track. is there. Such means is disclosed in JP-A-7-153045. In this publication, as shown in FIG. 1, an MR head which is a high-sensitivity type head is used as a reproducing head, and the center of the sensitivity distribution of the MR head is moved by a shift amount SL as shown in FIG. The distribution is located at an appropriate position on the track as much as possible.

However, when the center of the sensitivity distribution of the MR head is moved as the reproducing head, as shown in FIG. 1, the right tail of the characteristic curve is shifted rightward, but the left tail is still the same as before the shift. Is the same. That is, when the center of the sensitivity distribution of the MR head is moved, the skirt of the characteristic curve is widened. Generally, the reproduction output of the MR head is
A portion where the resistance value sharply changes, which exceeds approximately 感 度 of the sensitivity peak in the characteristic curve, is used for signal reproduction. The portion of the characteristic curve that is less than about 1/2 of the sensitivity peak is a portion that is not used for signal reproduction but generates crosstalk. Reference numeral 301 in FIG. 1 indicates a sensitivity distribution characteristic curve of the MR head before shifting, reference numeral 302 indicates a sensitivity distribution characteristic curve of the MR head after shifting, and reference numeral 3
03 shows a cross-talk region in the shift before the MR head, reference numeral 30 4 denotes a cross-talk region in the MR head after the shift. A crosstalk area 30 after the shift 4 is greater than the cross-talk region 30 3 before the shift.

This phenomenon is caused by using the MR head as a reproducing head to obtain a large reproducing output, but increasing the problem of crosstalk between tracks as a result of moving the center of the sensitivity distribution. Eventually, this becomes a factor that hinders a reduction in track pitch and an increase in track density.

Therefore, the present invention uses a GMR head composed of a spin valve type magnetoresistive element (GMR element), which will be described in detail later, as a reproducing head of the composite head, and moves the center of the sensitivity distribution of the GMR head. GM
By using the R head, a large reproduction output is obtained, and even if the center of the sensitivity distribution is moved, the occurrence of crosstalk between tracks is not increased, so that the track pitch is reduced and the track density is increased. To achieve. The present invention is focused on the fact that the sensitivity characteristic of the GMR head is symmetric, and that even when the center of the sensitivity distribution is moved, the entire characteristic curve moves without expanding the bottom of the characteristic curve. Reference numeral 401 in FIG. 2 denotes a sensitivity distribution characteristic curve of the GMR head before shifting, and reference numeral 40 denotes
2 shows the sensitivity distribution characteristic curve of the GMR head after the shift, reference numeral 403 denotes the cross-talk region in the shift before GMR head, reference numeral 40 4 denotes a cross-talk region in the GMR head after the shift. Region 40
3, 40 4 is only the same position size is different.

Further, even if the center of sensitivity of the MR head moves as described above, the shape of the sensitivity distribution and the width of the sensitivity distribution also change in principle. The movement of the MR head on the track is not bilaterally symmetric. That is, when the sensitivity distribution of the MR head is moved in the track width direction by a bias magnetic field or the like, not only does the sensitivity distribution necessarily change, but also, as shown in FIG. There is a problem that the movement of the moving is not linear.
This is significantly different from the conventional symmetrical movement of the reproducing head by the mechanical actuator, so that it is difficult to improve the performance of the magnetic recording / reproducing apparatus.

9 and 16 according to the present invention.
In the GMR head having the structure shown in FIG. 2, even if the reproduction sensitivity center is moved as shown in FIG. 11 or FIG. 18, a symmetrical sensitivity distribution is obtained as shown in FIG. It can also be moved symmetrically. Since the magnetization arrangement of both layers shown in FIG. 10 is symmetrical, the center of the sensitivity distribution can be moved symmetrically left and right when a bias magnetic field is applied. FIG. 4 shows the positional relationship between the bias current and the center of sensitivity. Compared with the MR head shown in FIG. 3, in the case of the GMR head, the center position of the sensitivity distribution can be moved linearly and symmetrically. As described above, the sensitivity distribution shape does not change during this movement.

An embodiment in which the present invention is applied to a magnetic disk device using a disk-shaped magnetic recording medium will be described below with reference to the drawings. FIG. 5 is a perspective view showing a schematic configuration of the magnetic disk drive according to the first embodiment of the present invention. A disk-shaped magnetic recording medium (hereinafter, referred to as a magnetic disk) 1 is driven to rotate by a spindle motor 2.
The magnetic head unit 3 is configured by mounting a composite head on a slider. This composite head is formed by integrating a recording head and a reproducing head at a predetermined distance in the track direction on the magnetic disk 1. The magnetic head unit 3 is disposed at the tip of an actuator arm 5 driven in a radial direction of the magnetic disk 1 by a coarse actuator 4. Coarse motion actuator 4
Is constituted by a rotary actuator using a VCM (voice coil motor). The composite head records and reproduces signals while being positioned on a target track on the magnetic disk 1 by the coarse movement actuator 4 and a magnetic fine movement actuator function described later.

Next, referring to FIG.
Will be described. FIG. 6 is a diagram schematically showing the principle configuration of the magnetic head unit 3. The magnetic head unit 3 has a recording head 11 and a reproducing head 12 which are composite heads. The recording head 11 is, for example, an induction type head, and records a data signal on the magnetic disk 1 by supplying a recording current according to the data signal from a recording amplifier (not shown) via a terminal 13.
The reproducing head 12 is a giant magnetoresistive head (GMR head) using a spin-valve MR element, which will be described later, and has a data signal recorded on the magnetic disk 1 and a data signal recorded in advance before recording the data signal. Reproduce the servo signal. The GMR element of the reproducing head 12 is supplied with a sense current I ₀ from a sense circuit (not shown) via a terminal 14. Further, a change in the magnetoresistance of the GMR element due to a magnetic field based on a signal recorded on the magnetic disk 1 is a voltage change due to the sense current I ₀ , that is, a voltage signal at the terminal 1.
4, and this voltage signal is supplied to a reproduction amplifier (not shown).

Near the reproducing head 12, the reproducing head 12
A bias magnetic field generating element 15 for applying a bias magnetic field for controlling the sensitivity distribution of the GMR element to the GMR element is provided. The bias magnetic field generating element 15 is supplied with a sensitivity distribution control bias current I ₁ as an external control signal from a current driver (not shown) via a terminal 16. Sensitivity distribution control bias current 1 _1, and track position information indicating a position of the track which the composite head is positioned as described below,
Control is performed according to head position error information indicating an error in the position of the composite head with respect to the target track. With this control, the sensitivity distribution of the reproducing head 12, particularly the sensitivity distribution in the radial direction of the magnetic disk 1, is controlled so as to optimize the relative positional relationship with the recording head 11.

FIGS. 7A and 7B show control examples of the relative positional relationship of the reproducing head 12 with respect to the recording head 11. FIG. FIGS. 7A and 7B show the recording head 11 and the reproducing head 1.
FIG. 4 is a diagram schematically showing a relative position change between the recording head 11 and the reproducing head 12 and a state of the sensitivity distribution of the reproducing head 12 when the reference numeral 2 is located on an inner track and an outer track on the magnetic disk 1. It is.

As described above, when a rotary actuator is used as the coarse actuator 4, the angle difference (skew angle) θ between the head direction (azimuth direction) and the track direction changes depending on the track radius position. In the present embodiment, the skew angle θ becomes negative in the inner track 17 as shown in FIG. 7A, and the skew angle θ becomes positive in the outer track 18 as shown in FIG. 7B. I have. As shown in FIGS. 19A and 19B, in the related art, the change in the skew angle θ depending on the radial position results in a track shift between the recording head and the reproducing head.

On the other hand, in the present embodiment, FIG.
As shown in (b), the magnetic sensing unit 19 of the reproducing head 12 moves in the track width direction indicated by an arrow by an external control signal based on track position information indicating the track radius position on the magnetic disk 1 where the reproducing head 12 is located. It is a moving configuration. The movement of the magnetic sensing unit 19 can prevent a track shift between the recording head 11 and the reproducing head 12 due to the skew angle θ. In addition, the magnetic sensing part 19 is the magnetic disk 1
Means a region where the output of the reproducing head 12 changes with respect to a signal magnetic field from the head.

As described above, in the present embodiment, a spin valve type magnetoresistive element (GM
R element) and the GMR head
By moving the center of the sensitivity distribution of the head, a large reproduction output is obtained with the use of the GMR head,
Even if the center of the sensitivity distribution is moved, the occurrence of crosstalk between tracks is not increased, so that a narrower track pitch and a higher track density can be realized. In this embodiment, the sensitivity characteristic of the GMR head is symmetric, and even if the center of the sensitivity distribution is moved,
It is important to note that the entire characteristic curve moves without expanding the bottom of the characteristic curve.

Specifically, as shown in FIG. 8, assuming that the distance between the recording head 11 and the reproducing head 12 in the track direction is d, the center of the magnetic sensing portion 19 of the reproducing head 12 in the track width direction (the center of the sensitivity distribution). ) By approximately d × tan θ, the track deviation between the recording head 11 and the reproducing head 12 can be made zero. Here, the interval d is known. The skew angle θ is defined by the length of the actuator arm 5, the arrangement of the center of rotation of the coarse movement actuator 4, and the track radius position where the head is located. The control unit, which will be described later, can accurately determine the moving direction and the moving amount of the center of the sensitivity distribution of the reproducing head 12 at each track radius position based on the interval d and the skew angle θ.

In this way, even if the skew angle θ changes depending on the track radius position, the track deviation between the recording head 11 and the reproducing head 12 is eliminated, and both heads 11 and
12 can always be accurately placed on the same track.

Next, specific examples of the reproducing head 12 and the bias magnetic field generating element 15 will be described with reference to FIGS. The reproducing head shown in FIG.
The spin-valve MR element 20 is a GMR head using the R element 20. The spin valve type MR element 20 has a pinned layer 21, which is a first magnetic layer whose magnetization is fixed in a direction perpendicular to the surface of the magnetic disk 1, and the magnetization changes by an applied magnetic field Free layer 2 as a second magnetic layer
2 is provided with the nonmagnetic conductive layer 23 interposed therebetween. In the illustrated example, a pair of leads 24 are connected to both ends of the spin-valve MR element 20 in contact with both ends of the pin layer 21 in the track width direction.
24b are connected to the pair of terminals 14, respectively.

Such a spin-valve type MR element 20 is known, and the pinned layer 21 and the free layer 22 are formed of, for example, C
The nonmagnetic conductive layer 23 is made of, for example, a Cu film. Here, the free layer 22 in the spin-valve MR element 20 is oriented so that the magnetization is aligned in the track width direction in parallel with the surface of the magnetic disk according to the conventional technique. With such a configuration, the signal magnetic field from the medium is applied to the MR element.
20 , the magnetization direction of the free layer 22 is determined,
Due to the relationship between the magnetization direction of the free layer 22 and the magnetization direction of the pinned layer 21, the electric resistance of the MR element 20 between the leads 24 changes. This is the giant magnetoresistance effect.

As described above, the free layer 22 is uniformly oriented in the track width direction in the conventional technique, whereas in the present embodiment, as shown in FIG. 10, for example, as shown in FIG. Anisotropically oriented so as to be magnetized in different directions.

On the other hand, in the vicinity of the spin-valve MR element 20, a bias current line 25 made of a conductive film corresponding to the bias magnetic field generating element 15 in FIG. It is provided along the width direction. Both ends of the bias current line 25 are connected to a pair of terminals 16 respectively. The bias current line 25 is for applying a substantially uniform bias magnetic field Hb in the track width direction of the spin valve MR element 20 and in a direction orthogonal to the track direction.

By doing so, the bias current line 2
5, the direction and magnitude of the bias magnetic field Hb applied to the spin-valve MR element 20 can be changed. Thereby, MR
The sensitivity distribution of the element 20 in the track width direction, in particular, the position where the sensitivity is maximum (the center of the sensitivity distribution) can be changed. More specifically, the center of the sensitivity distribution of the MR element 20 is shown in FIG.
2 is a position where the magnetization direction is orthogonal to the magnetization direction of the pinned layer 21. When the bias magnetic field Hb is applied in this state, the magnetization direction of each part of the free layer 22 changes by the vector synthesis with the bias magnetic field Hb, so that the sensitivity distribution center changes in the track width direction.

[0041] FIG. 11 (a), (b) , when changing the bias magnetic field Hb applied to the spin valve element by changing the direction and magnitude of current flowing through the bias current line 25, the track of the MR element 20 5 shows a change in sensitivity distribution in the width direction. As shown in FIG. 11A, when an upward bias magnetic field Hb in the figure is applied, the center of the sensitivity distribution moves to the right, and downward magnetization is applied as shown in FIG. 11B. In this case, the center of the sensitivity distribution moves to the left. By changing the direction and magnitude of the bias current in this way, it is possible to move the center of the sensitivity distribution by an arbitrary amount in an arbitrary direction in the track width direction. In addition, the sensitivity characteristic of the GMR head is symmetric, and even if the center of the sensitivity distribution is moved, the entire characteristic curve is moved without expanding the bottom of the characteristic curve. However, the occurrence of crosstalk between tracks does not increase.

By providing the free layer 22 with an anisotropic orientation having a magnetization distribution as shown in FIG. 10, the center of the sensitivity distribution can be moved as described above, and the sensitivity distribution can be reduced. It is possible to obtain a sharper sensitivity distribution while suppressing the sensitivity to a narrow range. In the conventional MR head, the reproduction track width (reproduction width in the track width direction) is defined by the read interval. However, by providing the free layer 22 with magnetization or anisotropic distribution as in the present embodiment, the read width is determined. It is possible to realize a reproduction track width narrower than the interval of 24, and it is possible to achieve a narrower track.

The reproducing head 12 comprising the spin-valve MR element 20, the leads 24 and the bias current lines 25 shown in FIG. 9 is formed as a composite head together with the recording head 11 on a non-illustrated insulating substrate by a known thin film process. It can be easily formed.

Next, the configuration of the control system in this embodiment will be described with reference to FIG. In FIG. 12, the MR element 2
In the case of 0, for example, a constant sense current is supplied from the sense circuit 31, and a voltage signal corresponding to a change in magnetic resistance due to a magnetic field based on a signal recorded on the magnetic disk 1, that is, a reproduction signal is output. This reproduced signal is supplied to the reproduction amplifier 32
After that, it is input to the data decoding unit 33, the PES demodulation unit 34, and the track position information generation unit 35.
The data decoding unit 33 binarizes the reproduction signal from the reproduction amplifier 32, performs data identification of “0” and “1”, and then decodes the original data. The PES demodulation unit 34 outputs head position error information indicating an error of a head position with respect to a target track from servo data recorded in advance on the magnetic disk 1. The track position information generating unit 35 similarly outputs track position information indicating the radial position of the track where the head is currently located from the servo data.

The head position error information from the PES demodulator 34 and the track position information from the track position information generator 35 are input to the controller 36. The control unit 36 controls a VCM driver 37 that drives the coarse motion actuator 4 and a current driver 38 that supplies a bias current to the bias current line 25. Hereinafter, an example of a specific control procedure of the control unit 36 will be described.

First, the first control procedure will be described with reference to FIG. That is, the control unit 36 first controls the VCM driver 37 when, for example, a seek command for a target track is given from an HDD controller (not shown) in step 101. With this control, in step 102, the coarse movement actuator 4 moves the composite head toward the target track on the magnetic disk 1. When the control unit 36 confirms that the composite head has been on the target track on the magnetic disk 1 by the track position information generated by the track position information generation unit 35 in step 103, the control unit 36 determines in step 104 the radius of the target track. From the position, the moving direction and the moving amount of the center of the sensitivity distribution of the reproducing head 12 are calculated. If it is not confirmed in step 103 that the composite head has been on the target track on the magnetic disk 1, the process returns to step 102. Next, in step 105, the current driver 38 is controlled so that a bias current corresponding to the moving direction and the moving amount flows to the bias current line 25. Thereby, as step 106, the track deviation between the recording head and the reproducing head is corrected,
The sensitivity distribution of the reproducing head is controlled.

In the above description, the moving direction and the moving amount of the center of the sensitivity distribution of the reproducing head 12 were obtained by calculation.
Instead, as shown in FIG. 14, a look-up table (LUT) 39 is built in the control unit 36A, and the moving direction and the moving amount of the center of the sensitivity distribution of the reproducing head 12 are determined from the radial position of the target track. , Table lookups. The look-up table (LUT) 39 stores the moving direction and the moving amount of the center of the sensitivity distribution of the reproducing head 12 corresponding to a plurality of radial positions of the target track in advance.

Next, a second control procedure will be described with reference to FIG. That is, steps 201, 202, and 206 in the second control procedure are the same as steps 101, 102, and 106 in the first control procedure. That is, the control unit 36 includes, for example, an HDD (not shown).
When a seek command for a target track is given from the controller, the VCM driver 37 is controlled first. With this control, the coarse movement actuator 4 moves the composite head toward a target track on the magnetic disk 1.

The second control procedure includes steps 203 to 20
5 is different from steps 103 to 105 in the first control procedure. That is, in step 203, the coarse movement actuator 4 monitors the distance between the position of the track where the composite head is located and the target track, that is, the position error of the composite head, based on the head position error information from the PES demodulation unit 34. . And as step 204,
When the head position error falls below a certain threshold value, a command to stop the coarse movement actuator 4 is sent to the VCM driver 37. In step 205, the composite head is stopped at that position, and the current driver 38 is controlled so that the head position error becomes zero, thereby controlling the bias current flowing through the bias current line 25.

By the control of the first or second control procedure as described above, it is possible to correct a track shift between the recording head 11 and the reproducing head 12 due to the skew angle θ, and to perform accurate data reproduction. .

[0051] In the above embodiments is used the bias current line 25 as a bias magnetic field generator 15 for applying a bias magnetic field to the GMR element 20, instead of this G
A similar bias magnetic field can be applied by the shunt bias effect using the current flowing in the MR element 20 itself. The configuration of the third embodiment is shown in FIGS. 16 and 17, and in FIGS. 16 and 17, the same parts as those in FIGS. 6, 9 and 12 are denoted by the same reference numerals. .

As shown in FIG. 16, the magnetic head unit 3 'of this embodiment has a recording head 11 which is a composite head.
And a reproducing head 12, and there is no bias magnetic field generating element 15 shown in FIG. Further, as shown in FIG. 17, the current driver 38A
, The bias current line 2 in FIG.
5. The current driver 38 is deleted, and a new current driver 38A is provided. This current driver 38A
Under the control of the control unit 36 ', the sense circuit 3 shown in FIG.
1 of a function, G MR device current for applying the same bias magnetic field and the bias magnetic field generating device 15 by the shunt bias effect in 20 (sensitivity distribution controlling bias current) G M
It has the function of flowing to the R element 20.

In the above embodiment, the pinned layer 21 of the GMR element 20 is uniformly magnetized in the track width direction and the free layer 22 is anisotropically oriented. The same effect can be obtained even if the magnetization is oriented as shown in FIG. Such an embodiment will be described with reference to FIGS. That is, in the GMR element 20, when the magnetization of the pinned layer 21 and the magnetization of the free layer 22 are orthogonal, the center of sensitivity of the GMR element 20 is determined. Fig. 1
As shown in FIG. 8A, a plurality of magnetizations 21a having different directions are provided.
When the magnetization of the free layer 22 is oriented in the same horizontal direction with respect to the pinned layer 21 having .about.21e, the center of the sensitivity distribution is determined at a position corresponding to the illustrated magnetization 21c. By changing the bias, as shown in FIG. 18B, when the magnetization of the free layer 22 is oriented in the same right-upward direction with respect to the pinned layer 21 having a plurality of magnetizations 21a to 21e having different directions, the sensitivity distribution is increased. The center is determined at a position corresponding to the illustrated magnetization 21d. Further, by changing the bias, FIG.
As shown in FIG. 8C, a plurality of magnetizations 21a having different directions are provided.
When the magnetization of the free layer 22 is oriented in the same downward right direction with respect to the pinned layer 21 having .about.21e, the center of the sensitivity distribution is determined at a position corresponding to the illustrated magnetization 21b.

As described above, by changing the bias, the center of the sensitivity distribution of the GMR element 20 can be changed, and the same operation and effect as those of the above-described embodiments can be obtained. Further, since the angle formed by the magnetization of the free layer 21 and the pinned layer 22 may have the same distribution in the track width direction as in FIG. 8, instead of giving the free layer 21 and the pinned layer 22 anisotropic orientation, GMR A similar effect can be obtained even if the intensity and direction of the bias magnetic field applied to the element 20 are distributed. In addition, the present invention can be implemented with various modifications.

[0055]

As described above, according to the present invention,
Realized narrowed and densification of the track of the track pitch, and a large reproduced output magnetic recording and reproducing apparatus capable of obtaining a, and it is possible to provide a reproducing head using a magnetoresistance element.

[Brief description of the drawings]

FIG. 1 is a diagram showing sensitivity characteristics of an MR head.

FIG. 2 is a diagram showing sensitivity characteristics in a GMR head.

FIG. 3 is a diagram showing characteristics of a bias current and a sensitivity distribution center in an MR head.

FIG. 4 is a diagram showing characteristics of a bias current and a sensitivity distribution center in a GMR head.

FIG. 5 is a perspective view showing a schematic configuration of the magnetic disk drive according to the first embodiment of the present invention.

FIG. 6 is an exemplary view schematically showing a principle configuration of the magnetic head unit according to the embodiment.

FIG. 7 is a diagram showing a relative position change between a track, a recording head, and a reproducing head and a change in sensitivity distribution of the reproducing head according to a track radius position in the embodiment.

FIG. 8 is a diagram showing a moving direction and a moving amount of a sensitivity distribution of a reproducing head.

FIG. 9 is an exemplary perspective view showing a specific configuration example of a spin-valve MR element and a bias magnetic field generating element used in the reproducing head according to the embodiment;

FIG. 10 is a view showing the magnetization distribution of a pinned layer and a free layer in FIG. 9;

FIG. 11 is a diagram showing a change in magnetization distribution due to a magnetic field applied to a free layer in FIG. 9;

FIG. 12 is a block diagram showing a configuration of a control system in the embodiment.

FIG. 13 is a flowchart showing an example of a control operation of a control system in the embodiment.

FIG. 14 is a diagram showing a control unit having an LUT in the embodiment.

FIG. 15 is a flowchart showing another example of the control operation of the control system in the embodiment.

FIG. 16 is a perspective view showing a schematic configuration of a magnetic disk drive according to a second embodiment of the present invention.

FIG. 17 is a diagram showing a control system and a magnetic head unit in the embodiment.

FIG. 18 is a diagram showing a relationship between a combination of magnetizations of a pinned layer and a free layer and a center of sensitivity distribution according to the third embodiment of the present invention.

FIG. 19 is a diagram illustrating a relative position change between a track, a recording head, and a reproducing head depending on a track radius position for explaining a problem of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magnetic disk (disk-shaped magnetic recording medium) 2 ... Spindle motor 3 ... Magnetic head unit 4 ... Coarse motion actuator (rotary actuator) 5 ... Actuator arm 11 ... Recording head 12 ... Reproduction head (spin valve type MR head) 15 ... Bias magnetic field generating element 17 inner track 18 outer track 19 read head magnetic sensing part 20 spin valve type MR element 21 pin layer (first magnetic layer) 22 free layer (second magnetic layer) ) 23 non-magnetic conductive layer 24 lead 25 bias current line

Claims (15)

(57) [Claims] 1. A recording head for magnetically recording a signal along a predetermined track on a magnetic recording medium, a spin-valve magnetoresistive element , and the spin-valve magnetoresistive element.
The spin valve type magnetoresistive element provided in the magnetoresistive element.
Applying a bias magnetic field to the spin valve type magnetoresistive element.
Magnetic field that changes the sensitivity distribution of the element in the width direction of the track
Means for applying a signal recorded on the magnetic recording medium.
A reproducing head for reproducing a signal , and applying the bias magnetic field to the spin valve type magnetoresistive element.
An external control signal to be applied to the magnetic field applying means.
Magnetic recording and reproducing apparatus is characterized in that a that the control means. 2. The reproducing head has a shunt bias effect.
Biases the spin-valve magnetoresistive element
A current for applying a magnetic field is applied to the spin valve type magnetic resistor.
Claims characterized by comprising means for flowing into the resistance element itself
Item 2. The magnetic recording and reproducing device according to item 1. 3. A predetermined track on a magnetic recording medium.
Recording head that records signals magnetically with a magnetic field, a spin-valve magnetoresistive element, and a shunt bias effect
Bias magnetic field to the spin valve type magnetoresistive element.
Sensitivity distribution of the spin valve type magnetoresistive element by applying a field
In the width direction of the track.
Means for flowing into the spin valve type magnetoresistive element itself,
To reproduce the signal recorded on the magnetic recording medium,
And the bias magnetic field is applied to the spin valve type magnetoresistive element.
An external control signal to be applied to the magnetic field applying means.
Magnetic recording / reproducing apparatus, comprising:
Place. 4. The control means outputs the external control signal
4. The magnetic recording / reproducing apparatus according to claim 1, further comprising means for changing in accordance with track position information indicating a radial position of a track on which the reproducing head is to be located. 5. The control unit according to claim 1, wherein the external control signal is
4. The apparatus according to claim 1, further comprising means for changing in accordance with head position error information indicating a position error of the reproducing head with respect to a track where the reproducing head is to be positioned.
A magnetic recording / reproducing device according to any one of the above. Wherein said spin-valve type magnetoresistive element, provided across the first magnetic layer whose magnetization is fixed in a predetermined direction, a nonmagnetic conductive layer and a second magnetic layer which changes magnetization by applying a magnetic field 6. The magnetic recording / reproducing apparatus according to claim 1 , wherein the magnetic field applying unit includes a bias magnetic field control unit that controls the bias magnetic field according to the external control signal. 7. The spin-valve magnetoresistive element includes a first magnetic layer whose magnetization is fixed in a direction perpendicular to a surface of the magnetic recording medium, and a magnetization in a different direction depending on a position in a track width direction. A second magnetic layer anisotropically oriented to be formed is provided with a non-magnetic conductive layer interposed therebetween, and the magnetic field applying means is provided on the spin-valve magnetoresistive element in a direction perpendicular to the surface of the magnetic recording medium. 6. A bias magnetic field applying means for applying a bias magnetic field oriented in a desired direction, and a bias magnetic field controlling means for controlling the bias magnetic field according to the external control signal. The magnetic recording and reproducing apparatus according to claim 1. 8. The apparatus according to claim 1, wherein said external control signal is generated based on a fact that an angle difference between a direction of a reproducing head and a direction of extension of a track changes according to a radial position of the track. A magnetic recording / reproducing device according to any one of the above. 9. A recording head for magnetically recording a signal on a magnetic recording medium along a predetermined track, and a spin-valve magnetoresistive element for reproducing a signal recorded on the magnetic recording medium. A reproducing head, magnetically provided on the spin valve type magnetoresistive element ,
Position between the track, recording head and reproducing head
A magnetic recording / reproducing apparatus, comprising: a conductive member to which a current is supplied in accordance with a specific relationship . 10. The magnetic recording / reproducing apparatus according to claim 9, wherein the recording head, the reproducing head, and the conductive member form a composite head. 11. A recording head for magnetically recording a signal on a magnetic recording medium along a predetermined track, a spin-valve magnetoresistive element, and a spin-valve magnetoresistive element provided on the spin-valve magnetoresistive element. Bias magnetic field applying means for applying a bias magnetic field to the magnetoresistive element, and adjusts the sensitivity distribution in the track width direction to the distance between the read head and the write head, the direction of the read head, and the track.
A reproducing head member that changes based on an angle difference from a longitudinal direction of the magnetic recording / reproducing apparatus. 12. A recording head for magnetically recording a signal along a predetermined track on a magnetic recording medium, a spin-valve magnetoresistive element whose sensitivity distribution changes in a track width direction, and a shunt bias effect. Means for applying a current for applying a bias magnetic field to the spin-valve magnetoresistive element to the spin-valve magnetoresistive element itself. angle between the longitudinal direction and the track spacing and reproducing head and the head
A magnetic recording / reproducing apparatus, comprising: a reproducing head defined based on a difference in degrees . 13. A reproducing head using a spin valve type magnetoresistive element for reproducing a signal recorded on a track of a magnetic recording medium, comprising: a first magnetic layer; a second magnetic layer; magnetic layer and a nonmagnetic conductive layer provided between the sensitivity distribution is varied depending on the position in the width direction of the track, before
The magnetization directions of the first and second magnetic layers are along the track width direction.
A read head , wherein the first magnetic layer is uniformly magnetized and the second magnetic layer is non-uniformly magnetized so as to be orthogonal at a predetermined position . 14. The first magnetic layer according to claim 1, wherein said first and second magnetic layers have magnetization directions orthogonal to each other at a center position in a track width direction.
14. The reproducing head according to claim 13, wherein the magnetic layer is uniformly magnetized in a direction perpendicular to the surface of the recording medium, and the second magnetic layer is non-uniformly magnetized. 15. The first magnetic layer according to claim 1, wherein said first and second magnetic layers have magnetization directions orthogonal to each other at a center position in a track width direction.
14. The reproducing head according to claim 13, wherein the magnetic layer is uniformly magnetized in a direction parallel to a surface of the recording medium, and the second magnetic layer is non-uniformly magnetized.